Now correct me if I’m wrong but im pretty certain I have heard the same news about Halo 3 a year or two ago. In an interview with IGN UK, Lars Bakken of Bungie said that the studio will not be making any more Halo games after Halo Reach, they also said they already have a IP in the works too.
After Reach that’s it for us. We’re already working on a new IP that we can’t talk about yet, I don’t know when we’ll be talking about it – when we’re ready I suppose – Lars Bakken.
This does not mean Halo is over though, there’s a chance another studio could produce Halo games after Bungie stops making the franchise.