Movies are not the comics. They cost tens of millions if not hundreds of millions to produce and market so Fox would be stupid to not reevaluate things as new information such as the success of Deadpool comes in.
Prior to Deadpool, all the info was that it was going to be a big budget 100 million+ PG-13 blockbuster which several people had questioned if that made sense. Now that Deadpool has shown you can do a modest movie with a 50-60 million budget with a R rating to boot then Marvel would be silly not to consider the impact that new information has on a Gambit film.
It also is quite possible, that they may figure they have the solo star to replace Wolverine now that Deadpool blew up so maybe they don't need a Gambit solo and they can simply just introduce him in a team movie like say X-force but there is no point worrying about that because that's just pure speculation right now.
By "Marvel", you surely mean "Fox", correct?
But I concur. It'd be absolutely ludicrous for Fox not to reevaluate their plans for the direction of the X-Men films. Who knows? This may lead to a complete genre Renaissance. Before Deadpool I think studios believed comic property based films had to be colossal budgeted, flashy, summer blockbusters to be successfully made. Using Deadpool as an example they may start green lighting more passion projects with lower budgets. Smaller budgets equal less risk of loss. But it could also be a start of over saturation of bad comic book movies due to a lack of vision. Teams like Ryan Reynolds assembled don't come along every day. To clarify, I'm not saying a comic book movie needs a big budget to be good nor am I saying low budget passion projects are the future. Just some possibilities that may come to pass thanks to this past February.
Hollywood heads have a pension for being copycat, boot licking cowards after all.