Gambit doesn't really need his own movie, IMO. He works better as part of an ensemble.
I don't have a lot of high hopes for that Kitty Pryde movie they just announced, either.
The issue with X-men is that the family/team aspect is what makes the whole thing work. The X-men aren't the Avengers and they're not the Justice League. Most of them weren't designed to function independently as their own characters with their own solo stories and rogues galleries. Thor, Captain America, and Iron Man were all their own characters with their own stories before the Avengers took off for example.
Wolverine and Deadpool are the exceptions since they're among the few characters to have any truly classic solo stories that stood the test of time. While there are definitely some solo stories/series that I like from the other characters (Lifedeath 1 and 2 for example), the rest of the X-men don't really have any objectively super-classic solo stories that measure up to the original Frank Miller Wolverine miniseries, or Barry Windsor-Smith's Weapon X, IMO.