Mine will be 3 in October too and we just went through this phase-- with no new baby or move. I think it is just a phase. We've moved back his bedtime to closer to 8 (we used to aim for 7:15) and after a morning or two I told him he'd have to stay in his crib until Mama came to get him. I will get him up at 7, but not before. We had one morning of a a big fit, but after that he went back to closer to 7 for waking up. i also made sure he had some toys and books in his crib so when he woke up he could look at them until I came to get him. It lasted about 2-3 weeks, and now sometimes I'll hear him between 6 and 7, but he seems to be drifting in and out.
I found that while he was going through this phase (which has repeated a couple times over the last 6 months) that he needed a morning nap for 45-1 hour in addition to the afternoon nap. When he got too cranky/disobedient (which he only does if he is tired) I put him down for a nap no matter whether he wanted to go or not. He usually screamed his head off for about 5 minutes and then passed out.
This too will pass. :-)