So, I'll join in the pessimism some more here: I honestly don't think the REAL Thor is coming back. I think Jane will still be Thor and the real Thor will continue to be Odinson somehow. OR, Odinson will be gone.
I think the upcoming Avengers movies are the setup for Marvel's next phase which is introducing the new heroes. The current actors are getting older, their contracts more and more inflated. From a business standpoint, to keep the fun going, Marvel has to do something. Getting different actors to portray the characters like what DC is doing over and over again doesn't seem to be Marvel's cup of tea. If this is true, there has got to be a greater than 75% chance the Thor in the Marvel movie universe will be Jane. Marvel thinks they need a Wonder Woman....well, there you go.