answered my own question.
So why isn't he in this, too? Well guess what, JCVD was actually offered a role from Stallone, but he declined. Why, you ask? Thanks to Total Film, we know the real answer.
Van Damme claims that Stallone was just interested in pitching money and action, not story. We've heard that The Expendables will have a lot of action, but as for story, at this point, who cares if it doesn't have an Oscar worthy story? "Stallone gave me a part in his next movie," JCVD told Total Film. "But I ask him about the subject, about the story. He said, 'You're gonna make lots of money.' I don't want to hear that, I want to hear what was my character. He was unable to tell what it's going to be. [Stallone said:] 'You know, uh, well, the fighting will be good.' [So I said:] 'Sly, what is my character?' So I didn’t do the movie."
http://www.firstshowing.net/2009/02/09/why-jean-claude-van-damme-wont-be-in-the-expendables/
That's funny as fuck. Jean Claude Van Damme of all people is worried about the plot!