If you need it now, then cancel the order, place a new order Tuesday early. If not in a rush and don't like risk, then wait until it shows up at Apple store and place your order then.
Bad advice.
If you need it NOW, go to the Apple Store to pick it up. If you don't need it for an undefined period of time, cancel the order and order it when you DO need it. It's not uncommon for new computers to take weeks to show up at the Apple Store after announcement (although not as often with simple speed bumps).
Still, waiting an undetermined period of time for an unannounced product for a computer you need now is silly. You buy computers when you need them or when there's a significant change in the value proposition that makes them attractive. This attempt to plan upgrades is silly.