If you are not special ordering the car, the deposit should be refundable. I would check with some other dealers. While I am not familiar with eastern Audi dealers, I don't think any of them are selling that many cars in this economy.
If the deposit is non-refundable, you should have a FIRM delivery date and, if the transaction is not completed, the contract is voided with full refund. I'm pretty sure that there are S5's available at western dealers ready for immediate delivery. You might check with an atty. to see if non-refundable is legal.
Of course, if the order is "weird", (an Orange S5 w/ a $30k turbocharger, etc), all bets are off.