I was having a think.
343 changed their Reclaimer Trilogy in to the Reclaimer Saga, as they did not want to limit their stories to just Halo 4,5 and 6.
So this would lead people to think there could be 7, 8 and even a 9 in 343’s vision.
“What’s the first story we want to tell and what’s the last story we want to tell.”
Originally, with the way that Spartan Ops expanded on Halo 4, I think that 343 planned to used Sp-Ops as a way to bridge the gaps between 4,5 and 6, making 2 if not 3 seasons for each game release.
However, with 343’s lack of interest in making a Season 2 for Halo 4, I think that 343’s intentions with Season 2 became so big that it would warrant a full game.
Hence Halo Xbox One.
Halo 4 had Chief vs Didact.
Sp-Ops gave us UNSC vs Jul and Halsey.
With the Didact speculated to return, I think 343 will save him for Halo 5, while using Halo Xbox One to expand on the Jul/Halsey dynamic while bringing Chief in to the fray.
With the little information that has been given about Halo: Escalation, I believe that Halo Xbox One will build off of the Sanghelios conflict detailed in the Traviss books and the new comic.
When Halo 5 comes around, 343 will lean more on the Greg Bear novels and who knows where the story will go.
With this in mind, I think 343 will stick to a 4 year development cycle for their numbered games while producing a game in between which will cover other events in the universe aside from the Didact.
Halo 4 - 2012
Halo Xbox One - 2014
Halo 5 - 2016
Halo (something) - 2018
Halo 6 - 2020
P.S. Can you give is the official title for Halo Xbox One for Chistmas, as that would be nice 
The story of Spartan Ops is being continued, more or less, in the ongoing Halo Escalation comic series.
And Halo: Xbox One continues John’s story, making it Halo 5 in practice if not in name. Besides, the original trailer for the game simply called it Halo 5 but they changed it at the last minute for unknown reasons.
It’s marketing. They’re calling it “Halo Xbox One” to hype the fact that Halo is continuing on the Xbox One and to give the aforementioned Xbox One more publicity and prestige, even though you’d think it’d be obvious. It’s just a gentle reminder that Microsoft is holding Halo hostage as their flagship title. 
I personally believe that it’s a marketing technique that will capture your attention.
Having it called “Halo Xbox One” rather than Halo 5 makes you begin to wonder. It makes you want to know more.
Your lust for information drives you to the word of 343i. They slowly spoon feed you information about this new game. As promising yet ambiguous features and ideas are given to you, you begin to want. You begin to need. You are excited for 2014. You are excited for Halo 5…
That’s all it is. They’re not giving us a title because it makes us want to know more. And when we do know more, we want to buy the game.
If it’s a marketing ploy then it’s certainly working. But whatever the reason for the name change may be, i do not think it will affect the final product. I’m fairly certain this next game was always meant to be Halo 5 and continue the Masterchief’s story.
The back of my halo 4 box already says “The Reclaimer Saga Begins”. 343’s halo being a saga is not a result of Spartan Ops.
Actually, if you look in the clouds when the trailer shows up, you can see that some form a 5 beside Halo, and no this is not because SpoPs, it already says Reclaimer saga on the back of Halo 4. I find it enough just to know that there’s more than just 3 new Halos.
The “Reclaimer Trilogy” was changed to “Saga” because it is more than just Halo 4, 5, and 6. It’s about everything that involves it. The video games, the novels (Kilo-Five Trilogy) and anything else that is set during this time.
There was a bulletin about this. There’s no conspiracy that “Halo Xbox One” is anything else besides Halo 5. That was all just poor marketing.
> The “Reclaimer Trilogy” was changed to “Saga” because it is more than just Halo 4, 5, and 6. It’s about everything that involves it. The video games, the novels (Kilo-Five Trilogy) and anything else that is set during this time.
> There was a bulletin about this. There’s no conspiracy that “Halo Xbox One” is anything else besides Halo 5. That was all just poor marketing.
So the Saga is the games plus other forms of media (novels and comics)? I’m sure there’s gonna be more than Halo 4, Halo 5, and Halo 6, being some spinoffs, much like the 1st Saga.
It just seems like a way to build hype to me. They probably think that people will keep wondering whether or not this is truly Halo 5, and then freak out when they find out that it truly is.
But it was obvious since the beginning that it wasn’t anything but Halo 5, making this whole thing a rather unneeded marketing scheme.
Its already been confirmed that it is a continuation of Master Chief’s story set AFTER Halo 4.
Sounds like Halo 5 to me even if they elect not to call it that.
You can see “5” in the sky at end of teaser trailer.
No matter what they call it, it’s Halo 5. We know that much.