I think King Gavilar was gay, Navani says that she had plenty of reason to cheat and that Gavilar was not the man Dalinar thought he was but that she missed him. It would also explain why Sadeas was so loyal to him and then to Elhokar if he was in a secret relationship with him (and I can really see this revelation coming out in an argument about loyalty involving Sadeas, Dalinar and Elhokar) also Sadeas having children is never mentioned. Just a theory but I think this could be a good way for BS to introduce a gay character that is key to the plot.
I also think that Kaladin will return to Hearthstone because Amaram will tell Sadeas about Kaladin after their first tense meeting (can't wait for that bit ), and as a way to get back at Kaladin, Sadeas will send people to kill Kaladin's parents (or something). After finding out about this Kaladin will go back home and hilarity will ensue.
Dalinar will die at somepoint, most likely after book 2 but you never know with Brandon.
Renarin will be important, no evidence other than Hoid taking an interest and now that he has just plate he may be like Dalinar was in plate (glowing like when he fought the chasmfiend), as I think he will be a radiant (also Syl didn't seem bothered by plate, perhaps blades of Odium and Plate of Cultivation)
Can definitely see Kaladin/Shallan or maybe a Kaladin/Laral after his return to Hearthstone (I also like a Renarin/Shallan/Adolin love triangle)
Some members of Bridge 4 will die (Moash?)
Sure Elhokar will die at somepoint
Would love it if Jasnah eventually held the Shard of Honour, having a heretic become a God would be hilarious