Assuming it turns out to be really good (I did not say better than Oot).
I think it will ride the Wii Success a bit, and sell over 8 million. The Wii userbase will be without a doupt over 60 million when it is released, and it will have Mega Hype surrounding it. Also, there is not much competition on the Wii for a game like Zelda.
Also... Although I hope this does not happen I think that Nintendo will do some things that make it appeal more to casuals (Hopefully this is just means Link can decorate his house... but it could also be a playable female charater... Maybe not Zelda, but someone new....)
I think this would bring things full circle, Brawl will be the best selling smash, MKWii will be the best selling MK, WiiSports will be the best selling game ever (also in Japan). The only major IP that would be the best selling is SMG (3d marios), but Mario 64 did come out a time when that genre (3d platformers) was at it peak. Also, If they made a new DK 3d Plat I think it would have trouble outselling DK64.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut
