Toby Jones stood out like a sore thumb in Captain America: The First Avenger. He was a highly respected actor stuck in the second-fiddle role to Hugo Weaving's The Red Skull, with the name "Arnim Zola," whom comics fans knew would eventually transfer his consciousness to a robotic body that menaces Captain America in the present day. We know he would be back. We didn't know that he was coming back right away, but that's just been confirmed by Toby Jones himself.
"It looks like I will be," Jones tells Hey U Guys. While that's not quite the same as a, "Yes, I'm in it, I carry the film in fact," he does sound confident in the linked video. If Arnim Zola returns, however, and the film takes place in the present day (as is the current understanding), then it makes sense that the post-World War II version of the character – complete with the creepy mechanical body with the distorted Zola face in the chest – would be the one used in Captain America: The Winter Soldier. And if Arnim Zola does return in this form, it also stands to reason that he could be the driving force behind the resurrection of Bucky Barnes as the film's main antagonist, The Winter Soldier. Zola is, after all, a super-scientist, and didn't Bucky go down in the process of capturing Toby Jones's character in the first film?
We're speculating about the plot, obviously, but it's a reasonable extrapolation based on what we have to go with. We love Toby Jones, we love robots, we hope this works out. What about you?