Remember, rebates are as much a fuction to get dealers to buy cars because they believe that will drive sales. The fact is that building cars people want to purchase will keep incentives down.
Don't forget that production is going to fall. There are products that don't have rebates and people are still buying them. Why? They are products that people want. With fewer retail outlets, less capacity to build, more of a dealers begging for cars rather than being begged to take cars will raise prices and reduce pressure for incentives. We may see a time when a manufacturer builds a car that doesn't sell and it's life span is killed rather than trying to prop it up with rebates.