In a recent interview with GameIndustry.biz, Phil Spencer, the head of Microsoft's Game Studios, said that there are more than three teams hard at work on various Halo projects.
That statement can certainly be interpreted a number of different ways, but it sounds as though there are at least four different Halo projects in the works at Microsoft's Game Studios.
Source
Q: So with the Age franchise, there's a strong echo of Halo, in that it's something you retain the rights to - you just don't need to own the company that's working on it?
Phil Spencer: Well, there's more than one team building Halo games right now. There are more than two or three teams building Halo things right now. Some of them we will own, some of them we won't. It's never been, for me, about who you own or don't own - it's about working with the best creative talent in the industry.
Phil Spencer: Well, there's more than one team building Halo games right now. There are more than two or three teams building Halo things right now. Some of them we will own, some of them we won't. It's never been, for me, about who you own or don't own - it's about working with the best creative talent in the industry.
That statement can certainly be interpreted a number of different ways, but it sounds as though there are at least four different Halo projects in the works at Microsoft's Game Studios.
Source