Of course, you are the best judge of your own child's ability and readiness. But, I want to weigh in with my experience. At our daycare, they transition from infant room to toddler room when 3 criteria are met: 1.off the bottle 2. walking steady 3. no pacifier. My girl was ready with all of these at 12 months on the dot (although she still tended to spend more time "scooting" and crawling than walking). After 2 weeks in the toddler room, she was a champion walker!
At our daycare, they do have a steady influx of babies, which may look like they're "pushing" the babies into the toddler room too soon. But, a closer look reveals that they will let the older babies hang out a little longer if they're not quite ready. In fact, they start the transition by letting the "almost ready" babies spend 1-2 hours each day in the toddler room, working up to half-days, until they are ready. That way, they get a good idea of what each kid can handle, and to help the transition not be so "traumatizing" for them.
As for the nap issue, I think they can adjust. The infant room had 2 scheduled 1-hour naps, but not every baby is going to sleep on that schedule. So, they'd always have 1 who wanted to nap earlier or later (or during lunch!), so adjusting to the 1 nap (2-hrs for toddlers) wasn't such a big deal. If you are really concerned, you should feel comfortable talking with the director and/or teachers (infant & toddler rooms) to see how they could compromise. For example, maybe your son could start spending the morning with the toddlers, but if he's ready for his morning nap at 10am, they could let him nap in the infant room. Same thing for his afternoon nap. Then, he could spend the rest of the afternoon in the toddler room again.
Good luck, you know your kid better than anybody, so go with your gut. But, don't count out the daycare. If you've been happy with them all this time, try talking to them and voice your concerns--see how they respond and if they're willing to work with you.