No one died in The Empire Strikes Back, unless you consider Dack or various Imperial officers "major characters".
If you don't think Ford's contract stipulated a one-film appearance, you're crazy. He may have had a unexpectedly good time doing the film, but his positive attitude this past season was likely because he knew he was finally free of the shackles of having to do any more episodes.
Yes, Luke will be prominent in the next film, but Rey and Finn are still going to be the "main" protagonists. Because if you give Luke equal time and show him throughout the film, people aren't going to care as much about the newbies. So he'll likely feature in the film's first half, and Rey will go off on her own to face Ren. She'll likely get defeated in the way Luke does in Empire, and he will perhaps have to give her additional training so she can emerge the victor in the final film.
The only weird thing with this theory is that having two people duel in three consecutive films would get a little old. They probably shouldn't have had a major face-off in The Force Awakens, one of many poor decisions made in the story's second half.
After a second viewing and much time to think about it, my biggest gripe aside from the lack of originality is the decision to end on a cliffhanger. It violates the "episodic" format and was really a cheap move to fire up the audience. Hamill should have never been advertised as appearing in the first film, and it should have ended with Rey, Chewie, and R2 going off to find him. The way they shot it, she gets in the Falcon and is seemingly there instantaneously, with no sense of a journey taking place, no build-up.
What I would have preferred is for Leia (who hugs Rey like they're family) to reveal Rey's relation to Luke after they meet. So not only is Rey seeking out Luke because of some mythology she's just become connected to, but she's now going to see her long-lost father. She gets in the Falcon, takes off, and roll credits. She's given between-movie time to reflect on the revelation, as is the audience. And it's a classic SW ending. The Force Awakens with that camera swirling around bullshit is so stylistically off from everything that's come before, which is unfortunate if they're all supposed to be part of one big story.