[quote name='SMMM']I'll laugh so hard if those techniques become completely useless in Brawl, and there's a good chance they will.[/QUOTE]
I doubt that it'll be taken out. There was L-cancelling back in Smash 64. It was done with the z button. Don't see as to why it should be taken out now.
And the pro game is very dependent on this and a couple other technical skills, it'd be very stupid to take it out and it'd most likely lose much of the smashing community.
Now as for wavedashing, that one is up there for the developers to handle. If they retain the physics of air dodging, then I believe it'll remain in the game. And if it is taken out, the competitive scene would prolly be hit hard, but I think they could certainly live without it.
But hey, I don't know anything, just speculation...
[quote name='Frazzle.D']
http://youtube.com/watch?v=4n4s5yB7ZkE
To this day, I still can't see how pros can press the L-Button a quarter of a second befroe they hit the ground with ease...[/QUOTE]
If you want to try, the usual input is this:
light tap x --> c-stick (any direction) --> down (on control stick to "fast fall") --> L trigger (as you hit the ground/usually right after down).
That video is very good, but I believe it doesn't add the actual manual input on the controller. And this of course takes much practice, and varies with character to character slightly.