They better have DLC possible for characters and stages. They've had time to learn their lesson from Brawl.
Also they better make sure they are able to patch the game for balancing in the all too likely event some characters are overpowered or useless.
I don't care about any other third party characters (if they're even going to do that again) other than Geno, but Snake making a reappearance would be cool. One of the things I liked about Melee was they had 64 stages included as unlockables and while Brawl had Melee stages there weren't any 64 stages. That was a disappointment.
I'm excited by the news and I'm interested in what kind of compatibility there will be between the Wii U and 3DS versions. But given the game isn't even in development yet other than MAYBE some early planning I'm going to not get too excited until I start seeing some actual trailers and gameplay footage.