Phil Spencer explains why Halo 5 probably won't come to PC
That's all well and good, but where's Halo 5? Spencer returned to his Frankengame analogy, explaining that Halo 5 was designed from the beginning to release for consoles. On the other hand, Halo Wars 2 was developed with both Xbox and PC in mind, and Spencer cited that as a reason for its success on both platforms. "In terms of Halo FPS on PC, I think there’s a ton of opportunity for us right now, but I don’t want to get into a world where we’re looking back, like at Halo 5. It doesn’t mean there’s nothing there that could ever end up on PC, but I’d much rather look forward with what our plans are."
http://www.pcgamer.com/phil-spencer-explains-why-halo-5-probably-wont-come-to-pc/