Someone named TheDuke1213 posted in the HBO forum that he'd heard a rumor there would be a huge add-on product for Xbox Halo coming out next year, including new multiplayer levels. He went on that it would supposedly be confirmed in the next edition of OXM. Matt shut that down pretty quickly:

Trust me: just because something is printed in a magazine doesn't make it true.

If we wanted to ship such an ambitious product in Q2 2002, we'd have to be working furiously on it right now. But we're not. And we're still not planning any add-ons for Xbox Halo.

Let's hope that's because they're busy figuring out how to bring Halo to the Macintosh and the PC.