...we just don't know what he'll be starring in yet. X-Men: Apocalypse? A solo film? The still-confirmed X-Force movie? I don't think Gambit was ever part of the X-Force roster, but Fox has shown they're not always 100% beholden to the source material on their Marvel properties.
In the quick red carpet interview with the producer, she also says she wants to work on Deadpool. Presumably that will also ignore his appearance in Origins: Wolverine, since they're pretty clearly ignoring Taylor Kitsch's Gambit at this point.