My two babies made the transition to one nap at around 15-18 months. All babies are different, but don't necessarily take his protests as meaning that he does not need the nap. Both of my babies have gone through phases where they would protest, but sleep is a non-negotiable in my book. He could be protesting just because playing is a lot more fun than sleeping, but sleep is a critical need for babies.
Again, every baby is unique, but this is how the transitions went with my two babies, just to maybe give you some ideas. With my first baby, he was taking longer and longer to fall asleep for his morning nap (he went to sleep on his own in his crib, but I always listened on the monitor and I could hear him playing). Morning nap was about 9-11am, afternoon nap was about 1-3pm. He would play during his morning naptime and sometimes not fall asleep until about 10:45, then sleep for his usual 1-1/2 to 2 hours (if I let him) but then would not be ready for an afternoon nap, and much too tired to stay up until his 7pm bedtime. So I would keep him up in the morning, give him an early lunch around 11:00 am and try to have him down for a nap at about 11:30/12:00. It was a difficult transition because he would get really tired and grumpy, but then he would sleep 2-1/2 to 3 hours during the one nap, and was pretty well set until bedtime. It took a couple of months before he completely adjusted to the new routine and no longer got real tired in the late morning.
With my second baby, he started sleeping for a really long time during his morning nap (it was usually about 1-1/2 hours and he started sleeping over 2 hours) then he would only sleep for about 45 minutes during his afternoon nap. So to me, that was the cue that he was ready for only one nap. His nap schedule was the same as my first baby's nap schedule had been, so I did the transition timing the same way. This was a really hard transition for him because he got soooo tired in the morning, so I would do a "sedentary" type of activity, like take him and his big brother for a walk in the stroller, or run an errand. Many mornings, he would fall asleep in the stroller or in the car seat (one morning he even fell asleep on my lap eating Cheerios! it was adorable!) and get a short "cat nap" - this seemed to work out perfectly. The short nap would rejuvinate him so he could make it until lunch then an early afternoon nap. It took him many months to adjust to only one nap a day, and I had to be very diligent to be sure he was in his bed for his nap no later than 12:00 (sometimes even a little earlier) because he was just too tired. He is now 28 months old and is lately able to wait until 12:30/1:00 for his nap.
So I hope that gives you some ideas. If now is the time, or it comes a few months later, good luck!