Gamescom Surprise: Halo Wars 2 Exists, Coming to PC
Not necessarily a "proper" Halo game, but we are indeed getting a Halo game on the PC, in the form of Halo Wars, a spinoff RTS that was originally exclusively for the Xbox 360 in 2009. If you haven't heard of the title before, don't worry, it wasn't particularly popular at the time, but it did present some interesting solutions to the question of "how do we make an RTS on a console work?" Namely, much of the involved base-building was removed, and you would construct nodes around a singular spire, much like in Etherium, now that I think of it.
Not much is known about the game at this time, as it's slated for a Q3/Q4 release in 2016, but an interesting point to note is that 343 Industries is partnering with Creative Assembly, perhaps most famous for their work on the Total War series, and also a little game called Alien: Isolation. Likely due to the fact that few at 343 have worked on an RTS title before, it will be interesting to see what this partnership means for the game, and its newfound home on both the Xbox One and Windows 10.