Nintendo still has several untapped franchises yet to be published for the Wii. While I won't say any of them will see the same response as say, Brawl, they will be enough to maintain interest for those primarily gaming on the Wii.
By the time those as of yet unseen franchises roll out, giving a rough two year turn around cycle for those franchises that have already been released, I would expect to see the next version of at least some of those games nearing gold status. Another Zelda, a new Metroid series, another Mario title, etc.
I'm sure most have noticed Nintendo is roughly releasing one major title per quarter this year, which is something that should be sustainable for the near future.
One thing that can't be counted on this year is for solid third party titles on par with Nintendo's key franchises. It's unfortunate for Nintendo fans, but third party developers simply won't sink their heaviest resources and their best development teams (spending years on a potential hit title) into Wii exclusive softs. And if they're not exclusives, it hardly needs to be said that the Wii version is simply a scaled down version of a game developed for the 360/PS3.
As for the whole doomsday scenario, it is about as likely as those who believe the market for the Wii can double, triple or more every year infinitely until it is replaced by Nintendo's next console.
That being said, I would not be surprised to see demand met for the Wii prior to Q4 2008, followed by a near complete sell through for Q4 and then settling into typical console sales rates by Q1 2009 with ample supply available. That is much more plausible than claiming something like the Wii will sell 50million by Q1 2009 and 100million by Q1 2010.







