Most retailers allow pre-orders until the midnight release. At times if you are buying a special collector's/deluxe edition etc of a game they may sell out but currently there seems to be plenty of stock of Morrowind CE across the board. As far as the base game goes you realistically won't see a retailer sell out.
I don't always drink Skooma, but when I do I go to the Southwall Corner Club. May you walk on warm sands my friends.