I can't remember my boys ever sleeping more than that. They both liked to take 3 hour naps, and would then sleep about 7 or 8 hours at night. I was so excited when they finally gave up that nap!
You really could try blackout shades! Since our boys are in school, we generally do not close the shades during the week so that the sun wakes them up. It's kind of frustrating during the winter months when we wake them up for school and they get mad because the sun's not up. We left them open just after the time change and were awakened by our 4 year old at 5:30 (I usually wake them up around 6:45). I just looked at him and said, "Do you want to watch Team Umi Zoomi?" Thankfully he said yes, and that bought me and my husband another 25 minutes of sleep! He was better the next day :-)
You can try the blackout shades. They really might help. Otherwise I would say you need to decide if you want to have a later bedtime in favor of a later wake time. But in the end, he probably is getting all the sleep he needs.