I don't know if you've seen the news yet, but Halo: Reach has just been announced at E3. Discuss! Ok, so maybe it's not exactly official...
If you noticed in the Halo: ODST gameplay trailer at E3, there was a point where it the guy looked on the wall and in grafitti it said "Remember Reach" So maybe Reach is like a prequel to the whole Halo Trilogy, or it's some sort of sequel to ODST, or it's a completely new add-on campaign focusing on some other different point in the halo trilogy. We know Bungie's making it so it's probably nothing like Halo Wars.
Actually during the Microsoft Keynote address, the announcer said that Reach would be set along the lines of the fall of reach book, placing it before Halo 1. Not sure on the relation between Reach and Halo Wars, mostly cause i havent played the latter.
Wrong section, and look before you post. http://www.forgehub.com/forum/halo-discussion/73575-odst-reach-news-thread.html