I know some fans are opposed to this but i truly feel GAMBIT has a place in this film and let me explain why.
Firstly there isnt much hope at all for a gambit spinoff and the Wolverine movie is a perfect way to introduce this character. Gambit is Canadian as well, so theres more of a reason to show up in a film about Wolverine wandering all over canada searching for his past.
Secondly, there are less characters in a spinoff than another x men ensemble, and this is a great opportunity to get gambit a lot of screentime and development, which may tie in with whatever they have in store for an x men 4 (which i doubt will occur for a VERY long time)
It just makes sense. With how the film universe never had an appropriate place to put Gambit, this one screams out. I dont know why fans think they can wait forever. They need to get started on Gambit.