Is Joss Whedon saving Thanos for the big finale in Avengers 3?

The Avengers 2 won’t come out until 2015, but we’ve already heard director Joss Whedon tease a brother and sister pair for the sequel, and I bet he’s not done teasing yet. In Whedon’s most recent interview with Desde Hollywood at a Iron Man 3 premiere, Whedon was asked whether Robert Downey Jr. would return to reprise his role as Tony Stark:

“I am not the guy who has to worry about him being replaced. He is Iron Man at this point. When I heard that he was cast I knew that something had just changed, and I usually don’t know stuff like that. I was like ‘Now we are in a new phase.’ The way he embodies it… I love working with him. He is so perfect for it, Shane captures it so perfectly in this movie.

I want him to play it forever. The great thing is that he has a flying metal suit. So it’s not like those Charles Bronson or Roger Moore movies where you’re like ‘Dude, you can barely stand.’ He’s got some fight in him. At the same time, if Robert decides to hang it up, he has a perfectly good excuse.”

Then when asked why the Avengers should be worried about Thanos, he discusses Thanos’ role, and how he’s saving him for the big finale:

“Well, Thanos is more powerful. He is so powerful, he is not someone you can just trot out and punch him. Like he did in the comics, you want him to be threading through the universe and to save the big finale for the big finale. He is definitely a part of what I’ve got going on. The thing about the Avengers is that they are very powerful, but they’re not very stable. So, there will definitely be some people that will shake them up in the next installment.”

So the idea that Whedon is saving Thanos for “the big finale” kind of suggests that he won’t be defeated until The Avengers 3, which would be the final chapter of Marvel’s Phase Three. This theory is made stronger by him saying that other villains will be shaking up the heroes in The Avengers 2. Remember when Whedon promised us death? That would surely shake up the team.

Does this mean the Avengers and whoever else they pick up along the way will team-up with the Guardians of the Galaxy for that big final battle against Thanos in Avengers 3?

Who do you think they’ll face in The Avengers 2 then?