Hmm... Put it this way... If Gambit ends up in the Deadpool movie there's no chance Feige will allow the writers/producers to damage the brand. It's why only the fringiest of fringe characters were heavily featured in those movies as gags. All the other characters were treated with respect or just made passing cameos.
Fringe characters: Bedlam, Shatterstar, Ajax, Negasonic, Vanisher, Rusty, Blk Tom, Copycat, Painkiller etc.
Mains (protected): Cable, Domino, Juggernaut, Colossus, whole XMA cast.
Gambit would fit into the later list. Used but held in high regard. Juggs got the hardest rub out of them, but he was also a villain - so, yeah.
If Disney plans on making money off of the Gambit brand - they'll protect it. Full stop. On the plus side, if Deadpool 2 is any indication, the 3rd will have a great budget. So any use of Gambit that is indeed protected, will undoubtedly look really good on screen.