I find it funny how half the people who post want massive changes, like new characters, new stages, and new features. There's a difference between an update and a completely new game.
SSB 4 discussion here:
http://www.smashboards.com/showthread.php?t=170103
As for updates, I still think the only thing that should change is making the 'special' stages playable... without gameshark (and in Final Destination's case, without crashing).
As for balancing out the game, if that were to happen, lots of characters, if not all, would need changes. All higher characters (not just Kirby) would need to be 'worsened', while lower characters would need to be improved. Here's my suggestion:
Pikachu have less priority
Kirby's up-tilt have less priority
Fox's lazers be similar to his melee's lasers (deals some damage, but no hit-stun).
Falcon's range reduced.
Puff have a better 5 jumps, rest does not send opponents as far.
Link have a better recovery (like up-B sends him farther, like his melee / brawl recovery).
Luigi have a slightly smaller short-hop.
DK's cargo release infinite be impossible to do. Attacks have slightly less start-up / ending lag.
Samus be less floaty and have usable combos.
Yoshi have some sort of third jump, maybe the same thing as brawl's recovery (up-B sends an egg, but rises Yoshi a bit).
Ness have less landing lag after his up-B.
Mario be... well, Mario. He seems to be fine.
If character updates like these were done, then they should be done frequently, continuouslybalancing out the new imbalances until the game is balanced enough... like they did with Starcraft.