Hi S.! My daughter will be 4 in Feb and we went through a similar period. Here's my take on it. He still needs a nap. Maybe not every day but he needs one. Don't give up. If he's occassionally insistent that he not nap then pop in Peter Pan and make him lay with you while you rest. But make sure he naps the next day. Bribe him if you have to - his favorite snack when he wakes up, a game when daddy gets home - whatever works. After a couple months, just when I was convinced that she was really ready to give them up, she's back to asking for them - telling me when she's ready to go down. Also, it's my opinion that you don't wake a sleeping child. If you don't have to be somewhere and he's not sleeping within 3 hours of bedtime then let him wake on his own. If he's still out then he needs the rest.
And finally, if he doesn't nap, plan to move bedtime up at least a 1/2 hour earlier. He may not appear more tired by his normal bedtime but it may be because he's already gotten a "second wind". If you catch him before it he'll go down a lot easier.
I'm guessing she was just going through a slow growth period or maybe it was just the time of year. I know some days it was becasue she thought she was missing out on something. If you let him stay up one or two days while you pretend to nap he may realize "this is all that happens while I'm napping?" and decide he might as well nap too if everyone else is doing it!
Hope this helps! Good luck and best wishes!