One argument for waiting until 2006 would be the release of the CableCard 2 standard, which should allow for pay-per-view and such. Also, given the horror stories I've read about people trying to get CableCard systems working, Tivo might be smart in delaying their release until the stuff actually works.

(Or, for all we know, they might have signed some kind of exclusive agreement with DirecTV that precludes them from coming to market any time sooner.)