Felix Salmon thinks we've reached it:
If we’ve learned anything over the past decade, it’s that things can stay at unsustainable levels for much longer than anybody might imagine. And over the medium term, it’s far from obvious that auto sales in the 9-10 million range are really as unsustainable as all that. Not only don’t we need to get back to “a typical replacement rate”; it’s actually very unlikely we will ever again see the rates of car ownership that prevailed before the crash. That was a world of 3-car garages in exurban McMansions; we’re moving into a more sustainable way of living, which involves fewer cars and higher urban density.
Ryan Avent has much more.