How can we know?
It really depends upon what happens within Nintendo, internally.
Project M's existence certainly shows Nintendo which game mechanics most of the competitive players thoroughly enjoy, such as smooth landing from L-cancels, and wave-dashing.
Crouch cancelling and directional influence are other Melee/Project M mechanics, but I personally don't care for them as much, as crouch cancelling gets me punished when Iand an attack. Whoops, sorry, won't attack next time.
Di is a fun metagame, but doesn't really make as much, or any sense.
Then gain, this is Smash Brothers.
A game where not even the title makes sense, as the game is not about the Mario brothers exclusively... Luigi is an unlockable character in the first two!