I imagine Bungie got pissed off with constantly playing second fiddle to COD on 360.
As for Epic, Unreal engine was literally the first thing shown running live on PS4, although that's understandable. As I recall, Epic announced Fortnite for multi-plat a long time ago. I wouldn't be surprised to see that as a timed Xbone exclusive, but you never know. I think Gears might be dead actually, or at least mothballed. Just my take.
Bungie and Halo is xbox. Gears is whatever. It sells great but it's no Halo. Would that kind of game even sell well on Playstation? (not saying they are bringing Halo over either lolnope)
All things being considered, no one could possibly betraylton Microsoft like Bungie could. I'm dying to see what they have to say on the SONY stage re Destiny.
I've already pre-ordered a Destiny PS4 bundle in my mind.