I read this rumor today but didn't even realize FIFA would become an Xbox exclusive, this one move would singlehandedly flip the european market and put Sony at a HUGE disadvantage. still we're talking about hundreds of bilions of dollars here, it's hard to say wether MS would attempt making such a move
There is no way Fifa would ever allow that. A reason why every major system gets at least one Fifa game is due to the Fifa organization mandated it. If Microsoft were to make it even just console exclusive I can see Fifa taking the license away from them.
Same goes for the NFL with Madden and Disney with Star Wars. There is no way those juggernauts would let those IP's go console exclusive.