Checked this out through work (obligatory reminder: I cover the gaming industry for a major media outlet). The rumors started because Prima added a listing for a Halo Deluxe Stratgy Guide (I forget the exact wording right now). This led to the Halo 2 early rumors - which are about as wrong as wrong can be, as that game has slipped until mid-year, according to developers I've talked with.
Phase two of the rumor was a revamped Halo, with a few new levels and the ability to play online. Easier to swallow, but also false. Microsoft would be cutting the legs out from under Halo 2 with that (and they've said this publicly).
It turns out that Deluxe Prima guide is just a revised version of their current guide, with extra material that relates to the PC version.
Sorry guys.
