I don't buy this. Maybe they've just been more prepared this time, but it did take a while for shipping estimates to change at all, even from the 16th. Now it's been a good six days before they all change to 2-3 week estimates. It seems like there's either less demand or more supply.
I can also see why previous iPad owners wouldn't be compelled to upgrade. As I've said before, I've been waiting for a "retina" or otherwise upgraded screen to come to the iPad before pulling the trigger on one at all, so it's a great product for me personally. Otherwise, moderate upgrades to internals and rear camera only, no true Siri (at least initially), and no improvement in battery life considering it has to power these new internals and four times the pixels... I can see why many would skip this round.
Still, it'll all come out when Apple posts its quarterly earnings.
You can still get them at various stores, though. I walked into Best Buy at about 7 pm on iDay last year and got the one I preferred (16 GB black). I didn't even have to wait in line. They had several left at that point.
I was in line at Best Buy last year and about 20 people behind me is where they ran out at. So it varied by store. But on line orders after about 2-3 hours of starting at midnight went to 4-6 week delays. That was my point. It was totally different than online orders this year.