First of all, we're not even sure if the law passes. It's been proposed every single Congress but got nowhere.
Second, even if it passes, Tesla will probably know before us and increase the price to keep some of the money for itself, like it already increased the price of MY by $1k.
I'd say if you need a car, buy it now. If you don't need it now, buy it later. Do not let the bill be factor in your decision.