https://www.pcgamer.com/halo-5-might-finally-be-coming-to-pc/

When Halo Infinite was announced for Xbox One and PC at E3 this year, we thought we were getting our first Halo (not counting RTS spin-offs) since the PC port of Halo 2. This might no longer be the case. Don’t worry, Halo Infinite is still on its way, but we might be getting another PC Halo before that with Halo 5: Guardians. 

The 2015 FPS has been re-released on Xbox One, but a recent change to the box art featured in the Amazon listing suggests that it might not be the only additional platform. Previously labeled “Only on Xbox One”, it has since been updated to read “Xbox One console exclusive”.