Wait, what exactly is wavedashing? I never learned what it was...
In a nutshell you air dodge diagonally into the ground which causes you to slide along in you're standing state.
A good wavedash happens when you input the airdodge before your character leaves the ground from the jump.
It's useful because it lets you cover a short distance while in your neutral state, so you can do any attack without the lag that comes from doing, say a dashing up smash. Since it starts with a jump, you can do it out of your shield too, so it's useful for punishing otherwise unpunishable attacks on block.
Some characters have better wavedashes than others though, it's based on the traction of the character. Luigi, for example, has perhaps the best wavedash in the game.
I'll admit it annoys me to see people be against wavedashing just because they don't like to or don't know how to use it, since I can do it but I don't since at the level I play (hint it's low) I don't need it nor is it useful, but it's not as if it affects me that it's there.
However in the context of wavedashing returning for this game I sort of understand the argument.
It's a matter of online play I think. Smash is, as we can tell from Sakurai's changes into Brawl, not meant to be very competitive. If wavedashing were to return then there's the risk of more casual players coming across competitive players who are capable of using that and other more advanced techniques and this might potentially ruin the experience for some.
Example, I like MVC. A lot. Super fun with me and my friends. However, I can't really play online because most everyone is so much damn better than me. This eventually caused me to sell the game because... well I just couldn't play it all that often unless I had friends around and we've all been more busy lately.
And it's not fair in the case of either game to say "oh well just get better, it's a fighting game what did you expect?" because I expected to be able to have fun playing the game without having to like... train for it.
Final SSB4 prediction/wishlist before E3 2013 http://imgur.com/2a4A1An