This C3 interview with Team 17 was conducted before Worms: A Space Oddity was announced. Still though, the answers to these questions seem to bode well for the Wii version being 2d.
C3: Have the team had chance to play around with a Wii development kit yet? And have you any ideas for bringing Worms to Nintendo’s new system?
T17: Now that would be telling! *smiles* Seriously though, we look at every new console as an opportunity to deliver more Worms fun to gamers. Wii is an exciting platform, so we’d be crazy not to consider it [ Since this interview took place, Worms: A Space Oddity has indeed been confirmed for Wii ]
C3: If you were to consider bringing Worms to Wii, would you stick to a high-resolution 2D style or go back down the 3D route?
T17: People seem to love 2D Worms and as our most recent forays into 3D haven’t been quite as successful as we’d hoped, we’re sticking to 2D for the time being.