Typically Apple does not have a clear out sale of old stock. 3rd parties such as Best Buy or other shops may. My guess would be Apple controls their own inventory so they don't just have millions sitting there in warehouses, and then the few they have left they use for warranty and other repairs. Usually the day of the launch the Apple Stores (at least in my area) already have new display models and their inventory is all new models. You may see a very minimal discount on their refurb store, maybe $50 or $100.
I actually bought my last MBP the first day they were on sale and while they had display units, I had to wait for the 10am shipment to arrive and be checked in before I could purchase. One person checked boxes as the shipper was unloading and handed them right to the people checking customers out.