I'm calling it now, Luke dies in episode eight. Sort of like how Yoda was an elder jedi teacher in his first appearance then dies in his second movie.
Leia IDK, I'm more worried about her than the rest. I think Ford and Hamill can pull off aged versions of their characters well enough, I'm not sure how they use Leia in this thing at all and I don't have much faith in Fisher. I'm really hoping that they are all more tangents than a big part of the main plot, sounds so far like the are integral but not the primary protagonists.
I'm least worried about Luke, I think Hamill will make a great older jedi master. I just hope they use all three of them as transitional and let the focus move to a new story. Really seems like that's the case which is smart, trying to use the old cast as main characters would have sucked.