In case you didn't see it, Tom McShea of Gamestop recently played a build of Smash Wii U and gave people 5 reasons why more of the 'same' is good.
https://www.youtube.com/watch?v=e0SvjuVbwLU&list=UUbu2SsF-Or3Rsn3NxqODImw
I'll list them for you.
1. Six years is a long time. (Referring to the length of release between Brawl and Smash 4).
2. There's nothing like it. (Playstations All Stars, Teenage Mutant Smash Up, Onimusha Brawlers are poor copies.) Also an argument against changing the formula too much.
3. Balance Perfection. (This one is the most lol.) He claims that Smash 4 is built for people who love balance, specifically saying that Nintendo is making this game for the Fighting Game Community. Obviously, the FGC, and specifically the Melee community would disagree at the moment. =P
4. The wrath of the scorned. Talking about how Brawl was bad, and this is Nintendo's opportunity to fix it.
5. Consumer demand. People like Smash for what it is. AKA, not making a Power Stone clone for the next Smash.
And I just realized after typing all of that, there is a Gamespot article that he also wrote on the subject. Doh.
http://www.gamespot.com/articles/five-reasons-super-smash-bros-doesnt-need-to-chang/1100-6421185/