People are also saying "MAKE IT XBOX EXCLUSIVE!" which would be absolutely stupid. Imagine if you're a mod developer on the PC and suddenly you can't develop mods for Minecraft anymore. Or you're a PS4 player and the game won't be updated anymore because Microsoft made it Xbox-only.
It won't be purely Xbox exclusive because now Microsoft will get royalties from all other versions of the game, so they will make more money that way anyways.