I wouldn't hold your breath for actual appearances of A-list superheros. I think the show wants to be its own thing and not rely on the popularity of the movies. Every once in awhile MAYBE there might be a cameo from what I read.
That doesn't mean there won't be a heavy tie in with the movies, through reference of events, and cross-over minor characters. I hear fall out from the battle of New York will have something to do with the pilot episode