I gotta throw my $0.02 in.
For the women, Dibaba will upset Keitany. Keitany is the most ruthless marathoner of all time, but Dibaba has really matured at the marathon and I think she might very well be realizing she can match Keitany. Watch for her to go with the pace and then hold on longer than Keitany. However, I don't think Dibaba has the pure grit needed for that men's paced WR.
For the men, it's still Kipchoge. He's the most intelligent, talented, and consistent marathoner in history. And he's still only 33. Unless you want to win big, your money should be on him, hands down. Remember, he has only lost once at the marathon, and it took a WR to beat him (and that was in 2013). Guy Adola is very talented, but this will only be his second marathon and does not know the course. Also, you have to remember how terribly inconsistent most big marathoners are. Expecting lightning to strike the same place twice (but this time it be a win) is a big ask (I feel anyway). Bekele will, of course, be a huge threat if he has to have a good day, something that has been really rare in his marathoning career. He will always be a wildcard. Just remember though that as he ages he will have far fewer good days of running.
Bottom line:
Men: Eliude Kipchogea in a new WR (2:02:25-2:02:30?)
Women: Tirunesh Dibaba (2:16?)
Those are my predictions/thoughts.