At E3 this year, Microsoft announced their Xbox Anywhere initiative, an ambitious cross play program that will put all Microsoft games on Xbox One and on Windows 10, allowing for cross compatibility between the two versions- to the extent that buying one version nets you the other, to the extent that your progress and Achievements across both versions are synched, to the extent that both versions will seamlessly interact with one another.
Now, Microsoft have confirmed that all games published by them going forward will be on PC, as well as on Xbox One- this means that Xbox will indeed have no true exclusives from now on (unless some third party developer decides to make a game only for Xbox in the future for some reason); it also means that highly vaunted Microsoft franchises like Halo shall be available on PC again at last.
So, when Halo 6 is eventually released? It will be on PC. Ditto with Forza 7. Ditto with any other Microsoft game you might care to think of. Now if only Microsoft would go back and release some older Xbox One games like Sunset Overdrive and Halo 5 on PC, too…