Originally Posted by Mr. Dent
^ I don't recall him saying anything about Thanos' role in A2. He said Thanos would be the mastermind of GOTG, and that they have plans for him over a long period of time. That doesn't necessarily disinclude him from only being used in post-credit scenes in other films.
It's in an IGN interview.
"Someone on the panel let loose that Thanos is a part of the movie and he is. Thanos plays a part in Guardians as a mastermind. He very much exists at a different plane than any of the other characters. We have big plans for him over the course of a long-long time."
Again, that sounds nothing like a credit-sequence. More like the "Emperor" treatment.