My guess is they would start around the number the insurance company would give you if your car was totaled.
Some call-in on a radio show was thinking she should get all her money back. Funny.
I think the answer will be somewhere between those two numbers. Obviously 100% back doesn't make sense (Unless you bought your car around last August, then you could argue that you tried to return it immediately and vw stalled).
Offering you straight depreciated value would drive me away from vw forever. I keep my cars for at least 10 years, depreciation at the beginning is brutal, but it averages out at the tail. If they offered me straight depreciated value (and I had to take it or fix the car), this would be the most expensive car I have ever owned. Over my typical cycle, depreciation works out to less ~$0.10/km, VW needs to get close to this to have a chance of avoiding horrendous lawsuits.