I'll be very depressing then leave the thread. DS is the same, tried the gro-clock with bribes / rewards for a year (he was 3/4) and it never worked. He unlocked it and reset it the second day ("mummy the sun is up!!"). I never cracked it, he has black out blinds and curtains, I've tried cooler room and warmer room, sleepsuits, different food etc.
He's 7.4 now and still an early riser, 6am on bad days even after an active day and late night (I don't have much tolerance for early mornings at weekends because I'm a LP). But he's big enough to potter in his room and play Lego when he gets up, he doesn't need me to supervise him. That said he still wakes me up early when he wanders to the toilet or comes into my room to tell me something.
I've told him he'll have a paper round when he's a teenager.