ya.... I asked at the el paseo store on Friday and they didn't know either.... I assume Wednesday for the stores....
I wouldn't rely on the stores having them in too early. Last year, I ordered my Air 2 online and popped through to a store the day after receiving it as they said they had received the Air 2 smart cases. The guy had to go through to the back to find the new cases but he asked me to check it was the Air 2 I had as the stores hadn't received any stock then. When I whipped it out the store staff were all hanging around to check it out! They had the cases but not the iPads!