After giving this some thought, I'll probably get the controller adapter but hold off on the controllers. I have 6 GameCube Controllers (four Wavebirds, two wired). The43 in excellent shape because I switched my original controllers for better ones in 2008 when you could find peripherals easily even after people moved on to new consoles.
A thought occurs to me.
As far as Smash Bros. goes, this is a pretty big deal.
If Nintendo was willing to let this slip early... what do they have saving for the main event?
It could be nothing. Nintendo tends to have uneven announcements. They're like a person who doesn't understand inflection so they emphasize the wrong words in a sentence. Then again, Sakurai is very good at hype (e.g. ending the Brawl trailer with Snake, the new games with Mega Man). He revealed a lot in the Smash Direct weeks ago which may be hard to top. An exclusive new mode is in the Wii U version could be interesting. Another third party character could be it though I can't think of one more desired than Mega Man.