As long as the X1X drops to $299 before then and it looks significantly better, then I'll get it for that. Otherwise, I'll just stick with the PS4P.
I may end up getting it for both, same thing with FC5 lol. I may want it on the One X if the graphics get a decent upgrade over the Pro although I'm not expecting higher end textures etc as that's not likely to happen but I'm sure the game will run at a higher resolution. MP will all be done on the PS4 Pro for me, none of the "friends" I had on XBL from the 360 days seem to have an Xbox One or X1X so I never see more than 1 or 2 people signed in tops at any one time and they are usually watching movies lol.