I doubt that. They'd be too caught up in the fact that they'll have smash on a handheld like they were a couple months ago.

It'll boost the Wii U about as much as melee boosted the gamecube.

A highly contentious notion, considering the fact that video games have become WAY more mainstream within the last decade. Smash Bros. and Mario Kart, as franchises, are also much higher profile now than they were on GC.

Mario Kart: Double Dash was an arguably "meh" entry in a popular franchise. Similar to Mario Sunshine and Wind Waker, it was a game that experimented with different ideas, which caused a lot of gamers to either love it or hate it. Aside from the addition of some BS power ups and the exploitable cheating potential of bikes, MKWii was all around a more accepted and popular Mario Kart game. And the franchise itself, thanks to the immense "expanded audience" success of DS and Wii, rose to a much bigger spotlight, which is why MKDS and MKWii both sold incredibly well. In turn, Mario Kart now has a much higher exposure to a bigger percentage of people, and given how good and fresh/inventive MK8 looks, that translates to a hype level that MK:DD couldn't have even hoped to have.

As for Smash Bros., you have to keep in mind that with Melee, while it was a great game, it was a sequel to what was essentially a late-entry sleeper hit on N64. The original Smash Bros. saw success, enough to merit a sequel, and it certainly was enough for fans to be hyped about Melee. But Smash64 wasn't a runaway smash hit. You could say that Melee was, and that's to it's credit. But in kind, the hype for Brawl was that much bigger, because Melee gained a lot of fans who had not played the original. Brawl in turn also sold conisiderably better, and along with the hardcore Smash fans, it like Mario Kart also benefitted, at least somewhat, from the "expanded audience" exposure. So I would contend that the level of awareness and perhaps even hype for Smash Bros. is also at an all time high, as compared to in the past.

What all that means, at least by my estimation, is that MK8 and SBU will in fact have a bigger impact on Wii U's console sales than Melee or DD did for the GC.

SSB is one of the only reason I'll be buying a WiiU.

The other reason is X

Oh and the other other reason is backwards compatible

and the other other other reason is still pending, but Nintendo will surprise.