0% Since September of last year on 2020 models and carried into the '21 models.
How long do they keep it? Who knows? I honestly don't see it sticking around because the market is stupid. Talking Hellcats: Incentives dropped from Power Dollars ($7970 Redeye or $7170 HC) for '20 MY cars to $6K for '21 MY. Either April or May this year it went down to $4K. Now it's at $2K. I could see them dropping the incentive altogether and upping the finance rate soon. So my belief is strike now if you can. But if you cannot, then best plan to buy with minimal incentive and at least some interest rate like 1.9 or 2.9%.
December is a long time from now. Consider where the economy was 6 months ago. That was before all the meme stocks and the major chip shortages.