Actually, you can expect the exact opposite to happen.
Workers will have 100% of their federal paycheck -- meaning that they will have anywhere from 60 to 100% more money in their paycheck than now. Prices will fall by about 20 to 30% when the plan kicks in because the imbedded costs of the current tax system will no longer be part of the car's price. The net result will be the car is priced the same including the federal tax and the consumer has more money to pay for it.
Changing to this form of taxation will generate more economic activity than you can imagine.
Please, do yourself a favor and read the bill and the research behind it. The bill is HR 25.
people will run out and buy cars before the tax hits - that's human nature, and that's the way consumers will behave. it happened in California when Davis went with his auto tax. it happened when there was a luxury tax on boats also.