In the majority of the threads I have read, everyone is merely speculating about characters already introduced to us as being the seven lights and only keyblade wielders in number 3. Although I too believe it will most likely turn out with Sora, Riku, Mickey, and the obvious others as being the only ones in the next game, i can't help but feel that there is room for others, possibly surprise chosen ones who we'd never been introduced to.

 

"Few Keyblade wielders remain now; I have heard of but a handful of others outside my circle. But the World is vast, and more of our kind may be out there." (Xehanort's Report V)

 

This leads me to believe that there are other masters out there with students of there own who could all very well be introduced to in the future. Again, I doubt that Nomura will throw this kind of curve ball at us, but hey, he did just include time travel recently soooo... Thoughts?

Good idea in the general sense of there being more Keyblade wielders that may be introduced later but, as you yourself conceded, its unlikely they'll be amongst the seven lights. I think it's more than likely that new Keyblade wielders will be introduced in the games after KH3 and the completion of the Xehanort saga.

well... it is a universe after all so...

Yeah, i bet there are more keyblade Masters and stuff around there, but i don't think any new masters and wielders will appear before/during KH3