I think everyone knows that Halo is Microsoft's big franchise, dating back to the original Xbox console. Because of that, we have seen Master Chief and crew appear on everything Microsoft related, from games on the consoles, to the Windows Store and Windows Phone titles. This is why it is a bit of a surprise to find out that the Halo series we saw at E3 might not be a Microsoft exclusive.
By this I mean that the new series, being produced by Steven Spielberg, might premiere on Showtime before on the Xbox Video platform itself. Now, this could all just be speculation, which seems likely as the entire reason they are producing original content is to prove that the traditional appointment television model is coming to an end. By premiering on appointment television they would simply be proving the model - the opposite of their goal.
On the other hand, with original series like Game of Thrones on HBO having such financial success, it could make some sense to run on Showtime, just maybe not as a premiere. If they were to premiere on both Xbox Video and Showtime together, those of us without subscription television channels could still enjoy the new show without the annoyance of having to wait, while people without an Xbox One could also enjoy the show, creating a better revenue model for Microsoft and the production team.
If they were to have a major win with a partnership here, it could definitely open the doors to rumored projects for Gears of War, Fable and Forza, which could all get their own programming treatments. This is in addition to the in-progress documentary series being produced for Xbox Video, with the first being about Atari, ironically. All of these projects succeeding would definitely push Microsoft's vision of upending appointment television for good.