From my experience stock is not usually held back by stores.
More commonly manufacturers, with big releases i have never seen much hardware stock if any come in early (by early i mean before its supposed to be sold). The only time i can say i've seen plenty of stock arrive before release is with games. I used to manage to warehouse in my old store so seen more than my fair share of deliveries come in. GTA san andreas for instance, we had loads of copies turn up maybe a week before release but this has never happened with hardware.
As far as i can remember when the wii was release we had i think 2 units turn up and again from memory i think these didnt show up till the day they were supposed to be sold.

I think we all just need to play that rather frustrating game of waiting for as long as it takes.