Yeah, who was ever thinking it would be an Xbox One exclusive? That sounds exceptionally unlikely.
The franchise is established on Playstation now, it's not a new IP that doesn't have a fanbase. Every release since ME2 has been cross-platform.
ME: Dentist will probably be exclusive to next-gen consoles, too, and the PS4 is outselling the Xbone by a fair margin.
The deal would have to be ridiculously good for EA to forsake the sales from PS4, and I can hardly see Microsoft paying that much money for Mass Effect. (No offense intended, but it's not in the same league as the exclusive DLC deals for Call of Duty or whatever)
It could be a "timed" exclusive like Plants vs Zombies Garden Warfare (where it sounds like they had to wait six months for the Playstation release), but even that sounds unlikely.
Shinobi seemed to have good information before, so I'm almost expecting an E3 teaser at this point. I think it's very likely to happen.