i wonder if he hasn't been getting his normal activity/stimulation the last couple weeks. have you tried tiring him out really good in the morning, coming home for lunch, and then a nap? i am a firm believer in naps - my son is 4 and we will continue to have naps for a long time yet - "I" need them, too! on the weekends anyway lol. and he is given a nap every day at preschool. there are some days that we have plans all day and he does ok without one, but the next day i make sure he gets one, otherwise watch out! he will be grump city.
in answer to your actual question, "quiet time" at our house usually turns into nap time. i use the term "quiet time" to encourage him to calm down and be still and not freak out thinking he "has" to go to sleep - he actually doesn't. depending on how tired i know he is, he will either take "quiet time" in his own room (and no i don't play music or turn on a movie or anything - if i know he's tired, he'll go to sleep) OR if i am pretty sure he isn't going to go to sleep easily, i will pull him into my bed and turn a movie on. i can keep an "eye" on him, and still get a bit of a catnap. my son is 4 though - at 2 1/2 naps were not negotiable. i'm not sure a 2 1/2 year old would lay quietly in bed for a movie. honestly i'm not convinced any 2 1/2 year old is "big enough" to give up a nap - but it all has to do with levels of activity. if they're not getting as much stimulation/excercise, then yes, they may not need naps as much. but in my experience the happiest kid is one that is worn out in the morning, and gets a good nap.