Re: X-Men: Apocalypse coming in 2016!
I'm not surprised that Brian and (maybe Laura) want Gambit in an actual "X-Men" film. XMO was just a tease and by putting him in this film, it'll do his character justice. They can touch on his relationship w/Storm (if she's in this), his cheeky past(thieve's guild), essentially he'll be the "Wolverine" in this film because that's the 1 thing FC lacked; that rebel character and he'll fit the bill perfectly.
As far as the 4 horsemen go, I think Magneto, Mystique, + brotherhood characters will sub as the horsemen (ala XME). If Mr. Sinister is intro. I'll be shocked (maybe he'll be a horseman). but I suspect Magneto eventually turning on Apoc just like in the epi XTAS "beyond good/evil" w/him wanting to be the only superior mutant n earth, blah, blah...
hopefully for the human side they'll intro. a younger Sen. Kelly, friends of humanity, maybe Henry Gyrich since his small cameo in X1 was blink and you'll miss it