I just tried going to the Apple online store (11:20PM Pacific time) and the store is unavailable - they are updating it. Could the update to the store be the new Penryn iMacs?? I guess we'll find out tomorrow...
given that the iMac is still outselling the updated MBP and supply seems steady, i'm guessing they'll probably hold off til montevina. the timing and supply works out much better that way