I hate to be the pessimist here, but Halo level anticipation? Really? You're talking about breaking financial records at that point. I'd say Guitar Hero III/Rock Band anticipation personally. Similar user base in the music fan area, and then it's got another crowd of folks (I'd say those who follow the works of Tim are about as populous as the Bemani crowd.) who will also be purchasing it regardless. Hopefully it gets some good press and enough hype to make it a big seller.
And I already see it's coming out next year 'round Xmas per gamestop.com (Did you pre-order to get a free shirt? Hmmmm?). Any ideas what it will be competing with?