Re: (Speculation) Captain America III: Fallen Son (The Death of Captain America)?
All I have to say is, if you don't think Marvel will setup Bucky to be Cap when Evans leaves for good, you're crazy.
Marvel Studios is known for taking risks above all other things. They put their faith (and money) in actors/characters that nobody knew or would've given the time of day to, and it paid off. Exponentially so. If anything, they're probably psyched to make the transition at some point down the road because they're going to build it up, foreshadow it, and eventually have it pay off.
I'm sure all the events of TWS were planned and considered years ago, considering Marvel has already planned out the next 7 years of films supposedly. If that's true, I can guarantee you they know what direction they're heading in with the various characters. I can't say for sure that they will do "Bucky Cap" but I think it sounds fair and reasonable to assume it's on the table since Evans will eventually drop out after Avengers 3 and that Sebastian Stan has a 9, not 6, movie contract (and has only appeared in 2 so far).