In an interview with IGN, Kevin Feige dropped some hints about some very iconic Marvel villains and their possible return in the MCU.
The first one to talk about was the Mandarin, about whom most of the fans where disappointing. However, Kevin Feige doesn’t dismiss the possibility of revealing the real Mandarin at some point: ”There have been [talks]. That’s one of the reasons we wanted to do the fun short that Drew Pearce wrote and directed. That was to clarify, ‘Hey, just because we did this thing doesn’t mean this other thing doesn’t exist.’ And as we were making Iron Man 3 — and I think Drew’s spoken about this — that was always our intention, was that Aldrich Killian was perverting the notion of these things he’s heard. There’s a little bit of that when he’s doing his detective work in his lab after Happy’s been injured outside the Chinese Theater. He’s talking about, ‘Okay, the Mandarin is taken from various iconographies and mythologies from across the world.’ The idea was always there was somebody like this. There had been rumors of somebody like this, and Aldrich Killian just built on that, to make his version.”
As far as the Red Skull is concerned, he has met his demise in a very ambiguous way in the ending of Captain America: The First Avenger. And even if Hugo Weaving has said he wasn’t interested in the idea of reprising the role, surprises may happen: “Well, the way we showed his ‘demise’ in The First Avenger was to showcase to people that he could perhaps pop up again sometime. I honestly don’t know when or where that would be.” As we understand it, he doesn’t know when and where, but he knows for sure that it will happen – after all, the Tesseract acted also like a door to another part of the universe.
The Mandarin and the Red Skull
Source: Comic Book Movie