The simple fact of the matter is that Brawl is going to be another Smash Bros. game. If it moves slower, so be it, but trying to make it appeal to wider audiences doesn't mean that it still isn't a Smash game.
I think that Melee appealed to a wide enough audience as it is. Sure, a casual player would look at you as if you were mad if you talked about wavedashing, SHFFLing, or any kind of Canceling, but the 8-year olds could still turn on all their items and have a fun time.
Brawl will be the same, but I think that if Sakurai truly has 'thought of everything' the core of the gameplay will still be capable of highly competitive actions. Melee isn't as competitive as it is by it's design, it's because the hardcore players have torn it apart and developed these advanced techniques and strategies.
In truth, the real reason that so many advanced things can be done in Smash Bros. games is just because of the percent system. In theory, you can always recover as long as you are crafty enough (obviously this isn't true because of spikes and meteor smashes and other such shenanigans) Since Brawl (obviously) still adopts the percent-based battle system, it will always have the ability to build and use the advanced strategies of recovery and edgeguarding that we use now.
Therefore, they would have to screw up royally to not make Brawl the same party game that it always was, and we would be irresponsible people if we didn't build the competitive game out of it that we did with Melee.
It takes a village to raise a fighting game.