During a press conference for Chinese Zodiac (CZ12), Jackie Chan mentioned that Sylvester Stallone has given him a role in The Expendables 3. It seems like the role will be meatier than a mere cameo. As Chan explained:
There's no official word on what Chan's role in The Expendables 3 will be. Ethan Anderton at First Showing notes that Chan asked Stallone if the third film will be a "buddy-buddy movie," which it apparently is. Anderton assumed this could mean Chan being a sidekick of some kind, but he admits it's just speculation for now.
As a long-time Jackie Chan fan, this is really keen news, and I think he should play a veteran Hong Kong supercop. If they can get Nicolas Cage, Cage should be his sidekick. Stallone is also looking to get Wesley Snipes and Harrison Ford involved in the film.