Wembley will be needed for the Olympic Football tournament which finishes on Saturday August 11th. The weekend after that is probably going to be the Community Shield between Premier League and FA Cup winners which is also held at Wembley. Be looking at late August for Summerslam to happen. It usually happens mid August.
Its been touched upon before a few times has this, because the Americans would have to watch the event on the Sunday lunchtime, but the European market has to watch at 1am in the morning!
Surely PPV buy rates would increase in Europe if it was on at a more suitable time.