I think it's possible. It's definitely going to be ridiculously huge and way bigger than Melee, just because the last 7 years of Melee tournaments have been attracting new fans like crazy. I saw a guy buy Melee the day the Wii came out. The game is a behemoth. It's definitely outselling Halo 3 overall simply due to the fact that it owns Japan and Halo doesn't exist there.
But this week 1.... no idea. I'll keep my fingers crossed.