Re: (Speculation) Captain America III: Fallen Son (The Death of Captain America)?
Crossbones and Agent 13 are long time members of Cap's supporting cast. I wouldn't take their inclusion to mean they're doing a storyline that both were coincidentally involved in.
The thought had occurred to me, however. Given Natasha's prominence and Sharon's lack thereof, one could imagine Marvel is going in that direction.
But it really doesn't seem like that good an idea.
People like Evans as Cap. Though at the same time, Cap isn't that big deal, at least not yet. In the comics, Cap has always been the elder statesman on the marvel universe. In the movieverse, he's just another superhero. Killing him simply doesn't have the impact it does in print.