Is Dwyane Wade still as fast as his younger self?
I think so. I've seen him go from one end of the court to another with speed that looks identical to Rose's.
Wade has only lost endurance, not speed. Wade tires out more quickly now and needs to conserve energy. So because of that, you are not going to often see Wade showing off why he was called the Flash.
Wade still has the very same blazing speed as he did when he was young. He just rarely uses it now.