The second installment hasn't hit cinemas yet, but there is already talk of another film in the insane, explosion filled Expendables franchise (it has two movies and a video game, it's a franchise), with producer Avi Lerner revealing one actor has already signed on, and talking about his wish list of other actors.
Speaking in a somewhat spoiler-ish interview with Total Film, Lerner revealed that Nicolas Cage has already signed on for the sequel, though his name is unknown, mainly because the interviewer dropped his dictaphone when it was said. It's something to do with Hunter. Other actors reportedly in the producers sights include Clint Eastwood (unlikely, but stranger things have happened), Harrison Ford, and Wesley Snipes, currently in prison for tax evasion, if he is out around the time of shooting.
Say what you will about The Expendables movies, but for me they are a giant slice of fun, crazy and mindless action. The actors involved seem to know this too, just having fun with the whole thing. As long as they keep making them, I will be there to watch them.