I am pretty sure that Joss Whedon won't direct The Avengers 3. I've heard rumblings from behind-the-scenes that he's pretty much finished with the Marvel stuff, plus doing two enormous movies like that in a limited time span is exhausting. On top of that, no director has ever worked with Marvel more than twice, and the only person who has done that was Jon Favreau, the first guy on board.
So if he leaves after The Avengers: Age of Ultron, who steps into Joss' seat for the third film? After seeing Guardians of the Galaxy and how effortlessly it combined humor and emotion and excellent large-scale action, all while balancing many characters, I thought James Gunn would make a good replacement. And Gunn is very happy working with Marvel - the relationship seems to be extraordinarily positive. When I talked to Gunn this weekend at the Guardians junket I asked him if he would be coming back for Guardians of the Galaxy 2 (the movie ends with a card that says "The Guardians of the Galaxy Will Return"), and he said he wants to. He said his contract has him signed up for a second film. Then he thought about it and corrected himself and said:
Actually my contract just says another Marvel film, it doesn't specify.
And so I took a leap and asked him, "How far along are you in negotiations with Kevin Feige to direct Avengers 3?" I have seen James Gunn in social settings and in press settings, and at this moment I saw James Gunn in one way I had never before seen him: speechless. He kind of sat there gobsmacked for a second. And then he said, "It was great seeing you!" as our interview time was up.