XBOX ONE has there killer instinct and SONY needs a fighting game and ED BOON has been giving more to SONY in the past like extra characters and skins for mk and injustice. If MK10 is a PS4 exclusive that would suck.
The PS4 is getting it's fighting game, just not anytime soon. Guilty Gear XRD will be a PS3, PS4 exclusive when the console version is released in the states. That game looks absolutely amazing. I am sure Sony will have more than it's fair share of fighters, considering how popular fighting games are with Sony's fanbase.
As for MK10 being console exclusive, I doubt it, but of course anything is possible. One thing I am sure you can count on is the PS4 getting console exclusive in game content. WB will likely remember how Microsoft turned it's back on them when MK9 was released(no ads from Microsoft about the game leading up to the release, no permission to use one of their characters) and how Microsoft turned it's back on Injustice to keep the focus on their game, Killer Instinct.
It actually terrifies me to think of MK10 as a console exclusive after seeing how things turned out for KI. KI would be so much more popular and widely played had it been multiplatform and a finished product. While MK10 would be HUGE on Ps4, more than enough to satisfy the pockets of WB and NRS....it would never reach the heights that it would if/when it's made multiplatform. I want the best for MK, so even though I already have a PS4 and do not plan on getting an XBone in the next few years, I want everyone who wants to get into MK to be able to.