During a past interview on AMC Movie Talk, Captain America: The Winter Soldier and Captain America 3 directors Joe & Anthony Russo were asked about if the possibility of bringing Red Skull back had been discussed.
"I think we heard that prior to our involvement with the project. I think we heard that they may have had that conversation at one point, but we weren't around for it, so it's hard for us to comment on it," said Anthony Russo.
Joe Russo said, "Specifically, the tone that we were chasing in that movie…I know we have a guy in a computer, but the tone we were chasing was sort of that conspiracy thriller. And we wanted to try and ground the movie as much as we could. And Red Skull, he's a fantastical character and didn't necessarily fit for Cap 2 and especially because it was about the fall of S.H.I.E.L.D. Certainly Hydra exists and that's his legacy, but there's something interesting about the fact that his legacy outlived the skull. And they're still dealing with the demons of it, but not necessarily him."
Joe Russo added, "That doesn't preclude him from returning, because he's certainly in the rogues gallery of Captain America characters. He's the preeminent figure, so that doesn't preclude him from returning. It didn't necessarily make sense for Cap 2 though."