I think it varies depending on the child. My 13 month old still takes two naps for about an hour each and really needs them both. (She sleeps 10 1/2 to 11 hours at night.) My neighbor however, transitioned her daughter to one nap at around 11 months as she seemed ready. She'd nap for 2 1/2 to 3 hours!
I agree with the early bedtime. An extra hour or so at night may allow you to push the morning nap off a bit, ultimately becoming one late morning/early afternoon nap and then an afternoon one. You can always experiment with it. Just try not to let him get overtired during the process. Let us know how it goes. I expect to be there pretty soon.