ds is in bed for 7.30pm most nights and gets up around 7am although he often gets up in the night for a pee so I have to help him in the middle of the night. He has a digital clock in his room and he knows he isnt supposed to come through in the morning until it says 7:00 - he has done well with staying in his room until then.
My DTs are 3.3. They go to bed at 6.30pm and wake between 7.30am and 8am, sometimes later if it's the weekend and we don't have to get up for any reason. I think they're fairly exceptional though - they've always been very good at sleeping (they take after me - sleeping is one of my all-time favourite things to do) They are at the stage where they do everything at 100mph, though, so I'm aware we might not be so lucky long-term.
DD is 3.2 and this past week we've been 'lucky' enough to have her sleeping for approximately 11 hours a night as she's been unwell. Ordinarily though she tends to sleep for no more than 9.5 to 10 hours a night regardless of what time she goes to bed. She has no daytime naps and hasn't done so since around a year old. She is full-on, on the go from the minute she gets up until it is time for bed!
My 3.3 year old goes to bed approx 7.30 and wakes up some time between 6 and 7. I haven't noticed that he sleeps later when he is more tired/had a later bedtime tbh so I am not sure your plan will work.
He knows he is supposed to stay in his bedroom until his clock shows him he can wake up (it is set for just before 7) but this is hit and miss whether he actually 'obeys' that rule
Generally has no naps during the day (unless we are in the car) either.