My 3 1/2 year old is exactly the same way! Any time anything does not happen as usual, he will speak up or try to correct it. That is all day long, and bed time is no exception. Advance notice is critical for our little guy. We made the switch to a toddler bed at 2 yrs 9 mos. I had planned to keep him in the crib until at least 3, but he had figured out how to climb out of the crib and the challenge was too exciting for him to resist. Then he would destroy his room. I wasn't worried about his safety. He is such a cautious kid, if he feels even the most remote sense of danger, he avoids it. But I expected him to stay in bed, and the prospect of climbing the crib sides was a temptation he could not resist!
This is how we made the switch. We had the bed in the garage (in pieces) and he had seen it before, and was very curious about it. A couple of days in advance, we told him we would put the bed together and that was going to be his new bed. It is a "fire engine" toddler bed, and he loves all moving vehicles, so this was terribly exciting. We talked about it several times and he was very excited about getting a fire engine bed! We put the bed together in the morning so he could play in it a little bit before it was naptime. The sheets, pillow and everything he liked to have in the bed was the same as in his crib. We talked about how he needed to stay in bed until we came to get him. Then we went about the usual routine. We still remind him everytime what we expect of him (stay in bed, be quiet - he has a tendency to exercise his loud voice while he plays before falling asleep) and it has been about 8 months now. It was a very exciting transition for him and it went very smoothly. He loves his fire engine bed! After a little while, he began to push the limit sometimes and get out of bed, but it's just a matter of obedience and a work in progress!
If you talk about it in advance with your son and he doesn't seem to catch the excitement, or he seems anxious about it, I don't think there is any harm in waiting a little longer, unless you have other reasons for needing to make the switch now. My son loved his crib, too (until he didn't love it enough to stay in it!:) and now he loves his fire engine bed.
I hope it all goes well! I would love to hear about it when you decide to go for it!