I've had winter tires on a BMW 3 Series in Frankfurt in July.

It was below 25 C but only just and they certainly didn't do the car justice.

So yes, you might, but I'd be quite surprised to see them and they certainly wouldn't go to any effort to give you the winter tires... it just might mean that they don't have a policy of taking them off.

Given the potential saving, I'd book the Audi especially as you might end up with just about anything (my money is on a Mercedes CLS wagon on German plates, although I've no evidence for that, they just seem to get everywhere!)