I'll throw out a couple that I didn't see anywhere (I skimmed through, so forgive me if they were...)
Josh Charles - He may be a bit old, but I like him, and JC is a great method actor, and can really pull off that whole "thief" feel I'm sure. Plus I'm still a fan of his from Sports Night...
Timothy Olyphant - For if they wanted a younger (but still older than the "X-Kids") actor for him.
Edward Burns - Again, big fan of his, as long as it's THIS look, not any of his others... He so impressed me in Confidence, that I think he's worth a look at casting if they want Gambit older...
Andrew Keegan - I dunno, maybe...
Yeah, I don't know too much about Gambit really (I'm sure it shows), I didn't read the comic too much or anything, but he was a favorite of mine, so I'd like to see someone good filling his shoes. Dorff and Michael Vartan are both good picks in my opinion, so if it's either of them...