It's a wildcard.
The game could blow up on handheld, or it could disappoint. We just don't know, because it's the first handheld entry. I'd say I agree the majority of people will prefer the console version, which will outsell the 3DS version, because of it being more of a console game by nature. Neither will beat Brawl alone though, but combined it should be possible.
Lifetime sales on 3DS: 5.2m
For the poll I guess 400k Japan first week.







