It was on wiki that I read Sly talking about Michael Biehn and Michael Pare. Personally don't wanna see Chan involved.
I think there should be more big stars in there just to kill off in cool ways one by one 'Aliens' style
Kurt Russell
Jai White
Leguizamo
Harrelson
Snipes
Casper Van Dien
Christian Slater
Paxton
Perlman
Trejo
Guy Pearce
Gerard Butler
Donnie Yen
Beckinsale
Jovovich
Charlie Sheen
Tak Sakaguchi
Cung Le
Tony Jaa
Iko Uwais
As military leaders, kingpins/villains or special ops leaders then you could use...
Eastwood
Peter Weller
Ford
Kev Costner
Bill Duke
Landham
Gibson
Cage
Banderas
Travolta
Seagal
Bruce Payne
Chiba
(some of these guys are too old for effective action, especially Eastwood).
End of the day there should only be one more in this franchise and it needs to have as many stars as possible even if it means bringing back Rourke and any others from number 2, any left alive eg. JCVD. So JCVD could be the bad guy again in the third but team up with whoever. If I was Sly I would take my time to ensure as many stars as possible, end of the day that's all these films are about, but to make it fun and interesting they gotta get killed off.
Originally it was only about the classic action stars together which was JCVD, Arnie, Sly, Willis, Lundgren and Seagal. We still have yet to see this. I'm amazed Seagal wasn't in number two.