does he still have 2 day sleeps? I found once DS moved to 1 sleep, he slept in much longer in the morning. you could try pushing his morning nap later, it may help push his whole day a bit later. So if he's going down for his morning nap at 8, slowly push it to 9-9.30. You could even try this if he only has one nap, i'm guessing he goes down pretty early if he's waking up at that time!