I wouldn't call the Pedi either - or at least, if you do, I should too.
My DS does the exact same thing. He goes to bed about 8 - usually will stay up playing and talking to himself until 9-10. He gets up around 7, pretty much like clock work. I've done everything I can - I've even taken the stuffed animals out of his bed and he still just "hangs out" and talks and "plays". He does usually take a 2 ish hour nap at daycare but doesn't really nap anymore on the weekends.
I can tell when he's tired and he'll go to sleep faster on those nights but for the most part, he's not tired at all during the day. I think this is just a case of when sleep patterns change. If he's not cranky, obviously tired, etc - I think this is normal.