I think that, given the popularity of a Jag/Jaina romance, that Jaina will, eventually end up getting together with Jag, as not only would it nicely explain the Fel dynasty's Force Sensitivity, but it would be nice for something good to happen to Jaina for a change - especially after the events of Invincible.
Plus, i'd like that to happen.
As to Kol's mother, there are a lot theories. Some people have said Tahiri - which, while a good choice, wouldn't necessarily be mine. Some people have even said Allana - but I don't think that would be a good idea at all. That said, it probably will be Tahiri - it's the only choice I can think of, unless they create a new love interest for Ben.
But that's assuming that Kol is going to Ben's son (I agree that it probably will be his son, but they might make him Ben's grandson - but I doubt that's possible in the timeframe set down).
But what i'd really like to know is... How is Luke going to die? We all know it's going to happen - but how?