Who ever said it'd be changed to one airdodge? Why not two or three? Why not one for every double jump? He hasn't decided yet because he's balancing it. If he adds Wavedashing back in, all his work for balancing would be completely undone. Would Melee's tier list be the same without Wavedashing?
"At this point the game will allow for multiple air dodges"
You can't have less multiple air dodges, It's either multiple air dodges or not multiple air dodges, no middle ground here.
(multiple=more than one, so if it isn't more than one than it can only be one or zero air dodges)
Who says he doesn't have wavedashing in mind when balancing? At the very least he can decide wavedash lengths if he adds them in, and he could change the length of a wavedash to suit each character in his eyes. You're just assuming things and trying to pass them as facts.
Also, I'm pretty sure Sakurai doesn't account for tier lists in his balancing, as he balances a character for multiple modes and player counts when designing characters.
Regarding tier list changes due to wavedashing, there are very little, i'm pretty sure the only character that received a significant enough boost from wavedashing to warrant a higher placement was luigi, hardly "undoing" anything.
And yes, There was a metagame before wavedashing, Ken was top player before wavedashing, and instead he dash danced. Heck, he even beat people who could wavedash before he even knew what it was.