I think it should lean more towards Melee than Brawl. Don't get me wrong, I want tons of stuff from Melee gone, like L-Cancel and some RNG elements, like Peach picking up bombs, Luigi getting missfires, G&W with his 1 - 9 hammer. There are several better ways to implement these things (like Project Melee did).
However I want it to be fast. It's very possible to make the new Smash game fast without L-cancel and Wavedashing, as long as the game promotes an aggressive playstyle the game will probably be fast (Brawl did NOT promote and aggressive playstyle). And I do want most recoveries to be toned down a bit, so that gimping becomes an important part of the game.
There are, however, some good things in Brawl I'd like to see as well. Buffering is a wonderful system, because it doesn't force player to be frame perfect with timing inputs after lag like Melee does. This is one of Melee's big problems, the character feels unresponsive for a lot new players because they input stuff during lag and nothing happends (I had some trouble with this as well when I first started to pick up Melee).
No matter how Smash 4 ends up, I'm sure it'll be a great game. I don't want Melee 2 or Brawl 2. If I want Melee I simply play Melee, the same goes for Brawl, and Smash 64 for that matter.