I'll start by saying I know this isn't really that early and there'll be loads of people on here with 6 year olds who have never slept past 5am and you of course have my sympathy...
Anyway, my three year old (will be 4 in January) has always been a great sleeper. There were times as recently as July when I'd have to go in and wake him up because it was nearly 9am and he was still snoozing.
Sometime around the end of July/early August he started waking up around 6.30-7am and immediately shouting for me or his dad. We used one of those "ok to wake" clocks and although it made no difference at first, he's now mostly staying quiet until 7.30 when it changes colour, thanks to a reward chart.
However he's still waking at the same time, he's just staying quiet in his room. But he's constantly really tired. He goes to bed at about 7, asleep for half past so he's getting 11-11.5 hours sleep. He refuses to nap, although we do generally manage to get him to nap for 45 minutes on a Sunday which seems to help a bit.
He started pre-school last month and that's made him more tired. He previously did two non-consecutive days in nursery and now does 4 consecutive, albeit sightly shorter, days at pre-school, so by Thursday evening he's ruined. We thought this might make him sleep longer in the mornings, but it doesn't seem to have made much difference.
Has anyone's children done anything similar and did they ever go back to sleeping in again? I'm not really that worried about how it affects me, I'm up by that time anyway either for work or with his younger sister, I'm just worried he's going to be tired forever if he's always up early.