"Iron Man 4" is still up in the air. Even if it happens, there are still many questions on the details since nothing has been finalized yet. Nothing except the villain?

According to Kevin Feige, the worst implications of "Iron Man 3"-that the Mandarin does not actually exist in the Marvel Cinematic Universe, is not the case. It has already been teased in the Marvel One-shot "All Hail the King" with Ben Kingsley reprising his Trevor Slattery role.

Writer/Director Drew Pearce has confirmed that in EW:

 "Imagine a real terrorist organization whose beliefs were long held and religious for thousands of years, and imagine a drunk, British actor coming along and essentially telling the world that he's the face of your organization. I think they would be right to be quite angry."

So there is an actual Mandarin-and he's actually peeved. But Pearce is not exactly an authority on these things, and the buck does not stop with him. To have further confirmation, Marvel President Kevin Feige clarifies with IGN:

"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."

From the line "that was always our intention" it means they did not rewrite Mandarin just to apologize to the fanboys who had strong reactions to the Trevor Slattery reveal.

Feige elaborates: "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."

We should await the further implications of this revelation. Every villain needs his hero, and the Mandarin has only one archenemy-that's Iron Man.