Microsoft hasn't had a mainstream PC release of Halo since the Halo 2 after which the franchise went Xbox Exclusive disappointing countless PC gamers who had to choose between buying an Xbox 360 or leave the flagship FPS title altogether.
The last Halo game for PC was the Halo Spartan Strike which was a twin stick shooter set in Halo universe and was a successor to Halo: Spartan Assault.
Recently in a live stream with Gamesradar, Halo Franchise Director Frank O'Connor hinted at a minuscule possibility of a PC port. When asked about the chances of Halo 5 appearing on PCs, he said that there's "plenty of chance" for Halo 5 Guardians to appear as a PC port. He also said that this would only help in their endeavors for blending the Xbox and PC gaming platforms and communities together.
He said:
Microsoft has made a huge commitment to normalise the Windows experience across multiple platforms, so you're seeing elements of Windows 10 are going to appear on the Xbox and Cortana and stuff like that. There is plenty of chance that Halo 5 could appear on the PC.
There's nothing new to announce at this point, but it's absolutely not out of the bounds of reason, and we developed the game on an Intel platform, so it wouldn't be the hardest thing in the world to move it to PC and take advantage of PC stuff.
Heads Up
Halo 5: Guardians is an upcoming FPS game in the Halo franchise, a sequel to Halo 4, published by Microsoft Studios and in development by 343 Industries. This game is set to release on October 27th, 2015. The game is Xbox One exclusive for now and promises to deliver a constant 60 FPS gaming experience with a brand new multiplayer mode called the WarZone that will support up to 24 players.