New interview with Joss regarding "Thanos":
"Thanos is more powerful. He's not someone you just trot out and punch him. Like you did in the comics, you want him to be threading through the universe and to save the big finale for the big finale. He's definitely a part of what I've got going on. The thing about The Avengers is, that they are very powerful, but they aren't very stable. There'll definitely be some people who are gonna shake them up in the next installment!"