This was done to foreshadow Baek Ah future marriage with Wooks younger daughter.
I posted this in feeds but I copy paste it here with some aditions: 

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Wang So (b925-r949-d975) has 5 kids, 2 sons ( one dies early) and 3 girls with her half-sister Queen Daemok who was sister of Wang Wook.
Wang So son becomes next, 5th king.

One of his daughters becomes Queen Mundeok, wife of 6th king, Wang Wook son.

Son of Wang So (b955-r975-d981) marries older daughter of Wang Wook, they have one son(b980-r997-d1009) who becomes 7th king but looses throne bc of his mother and Wang So direct bloodline dies out.

Wang Wook (b???- d969)has 1 son and two girls, he marries his half sister too
Son of Wang Wook(b960-r981-d997) becomes 6th king but doesnt have sons, only 2 girls. Wang Wooks direct bloodline dies out.

Baek Ah marries younger daughter of Wang Wook and has son (b992-r1009-d1031) who becomes 8th king.and first son of his son aka grandson becomes 9th king and seconds grandson becomes 10 th king. 

All next kings in Goreyo are descendants of Baek Ah. 
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In drama they speak about Wang so sons 1. birthday aka it is 956 ....So scene of Baek Ah meeting Wook must happen after 960 but before or at 969.
So more or less we can speculate that Wook married  after 949 but before 960


From Koreans point of view this foreshadowing is important moment. they even messed up littlebit actual timeline of events to show this moment.
Creators of drama just made up some details to make feel of fate stronger. I mean talisman and girls name....she isnt incarnation of  anybody.
When Wook dies his son is 9 yr old...so, daughters must be younger.

It wasnt told that Wook married again but it was kinda obvious that this happens when he is sent to exile.
No chances to be part in palace politics itself ,it is logical that he starts think about kids aka next generation.
Add here that Wooks sister cut off ties with her family - it means family needed more power to survive.
Marriage was best way to gain it.

 In international version there is one scene more when Wook has talk with his mother about kids and future and going to 1. birthday of Wang So son.But here is error - in 956 Wook doesnt have kids yet.

So when Baek Ah comes to Wang So and tells that Wook is dead - it is 969.....6 yr before Wang So death.
I heard that theres  going to be a new special but only on dvd true?
For now nobody knows.

There is out petition for  DVD/Blue-ray release with complete story ( all scenes from both versions) and some cut off scenes what didnt aired.

Tthere is out petition for 2. season.

It is up to creators and makers to deside what they do. No offitcial statements are given yet. 
Lets wait and see.
IU posted on her instagram a photo 
I don't want a second season. I just want one special, even if it's under a half an hour long of them meeting in the future. It doesn't even have to be canon, and I could even treat it as AU fanfiction. I just want to see that deleted scene :'( 
Season 2 is unnecessary. The drama was written and meant to it that way. why hoping for a happy ending? It'll never happen, so MOVE ON. If it's going to be a happy ending, the GREAT WRITING aspect of the story will be affected! 

What's good about the story and how it ends? The writers gave you an open ending which meant for you to conclude on your own as to how you want the story to end.

2 words for MOON LOVERS fans.  MOVE ON!

The drama was intended to leave a SCAR on your HEARTS!!!!
@raincat- I disagree about the reincarnation. Afterall, reincarnation is a major point in the original story. It was just not as heavily emphasized here in the Korean version. However, we already know that Soo's soul was tansferred back to her former life in Goryeo period. Next, there is Ju Mong and his future life. Also, the little boy she saves from drowning in the beginning right before she leaves, is same little boy who was child 10th Prince. (10th Prince was the first one she encountered when she came to in the royal bath.) So, although reincarnation is never literally explained, it is instead very obviously portrayed throughout the story. Therefore, it makes perfect sense for Wook's daughter, Baek Ah's future wife, to be the reincarnation of his first love. Her name, her attitude, her scolding to him and her trinket were very obvious hints that was the case. Sometimes, things do not need to be said in a story outright, but implied. :)
This 10 th prince part is pure fantacy of fans. Nice one but still...

Like you see all incarnations take place in faaaar away future... if follow the rule - this girl isnt incarnation but just future Queen and mother of kings who rule centuries. And it doesnt go with story logic. Why? Bc all incarnations happen in distant future in this story, not just after few years.And not only far away future but they ALL are have reincarnation with same interval and are living in same era again:

Ji Mong
Hae Soo
Wang So

(....and Ji Mong hinted that king Taejo also is in this era and he returns to him from past.)

What has Baek Ah done so evil that he cant have incarnation with them?
Nothing, so we can expect him to be there too.....so why not allow his beloved one to be there too? He grieved for her not less than WS for HS.

You know - history repeats itself, sometimes in rounds, sometimes in spirals.. 
Maybe I missed this part of discussion somehow, but why there were 2 incarnations of JiMong in the future? The first one as the homeless drunk man, and the other one as the professor? Or was it the same man?
I think I would be happy with a 'Special Episode' with happy Wang So and other prices ending... It would be a bonus if they showed reincarnated brothers in the modern world. But I agree with most about Season 2 being unnecessary, it would certainly ruin it. 
@raincat- Um. I am really confused by your last post chingu. :p First of all, just because Baek Ah's love of his life is reincarnated tgen doesn't mean that she can't be reincarnated in modern times, as well. It is never stated anywhere that these are the only two time periods where their souls are present. They are just the only two *shown*. Do you know anythibg about reincarnation? Anyway, it's beside the point because the ending was left open, though Wook's daughter being a reincarnation seemed pretty obvious to me.

@CherryBunnyI think we just look things differently but this is ok.  For me it was just foreshadowing of future, about actual history - for you it was incarnation  of his beloved. But both our views might be right, only creators know what they meant with this scene. :D

It has been mentioned in many dramas and movies that in Korea they believe that person reincarnate not earlier than after 400 yr, it might be even later.
I havent researched why, I just accepted it like it is. so I might be wrong.
About other Asian countries I dont know does they have any time limits or other limits.....but this discussion raised mine curiosity if I have bit free time I look into this deeper. It is interesting subject.

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@VioletSakura...no, there isnt two incarnations of Ji Mong.  In first episode we saw "beggar Ji Mong" and then HS goes to past and makes some changes, tiny-tiny changes and when she comes back we see in last episode that Wang So isnt remembered like "bloody king who killed his brothers and family anymore but like wise and strong king who started many reforms and build strong country....and "future Ji Mong" is clean, groomed guy.  Future has changed....so has Ji Mong.

There was one very good post in Soompi about theory that Ji Mong  is "Trickster" and some things what he told in past and in future to HS kinda prove it.

( about Trickster you can look up in wikipedia)
@Raincat, then what about HasSoo's life, why didn't her life change in any way? She was the same, had the same profession...
@raincat- I don't know about that 400 year reincarnation thing. I have never heard of it before. I can think of one K drama that has reincarnation of main characters, though, that are both reincarnated in very next generation. So if there is a 400 year belief, they certainly didn't adhere to it there. :p
@VioletSakura  They didnt show much to make any big conclusions but......

HS in first episode has lost her home and all money - she was in deep depth and chased by upset ahjummas, she was homeless and dirt poor drinking soju in park. 

HS in last episode woke up in nice home, she had coworker who cared for her, she was a lot of time in hospidal, yet she seems manage her life well.


Yes, her job is same but this was job what she likes from start, nothing wrong that her job havent changed.

Maybe there is more what is changed or not changed in her life but that isnt main point - she didnt tried in past change HER own life better but she wanted to change WS to be better king and she made it. Better king means better life for people and better future for country.

What is better in SHR future might be tiny-tiny but that tiny-tiny might be sometimes pivotal for in someones life and same time not so pivotal in other persons life

/just mine thoughts./