Nothing is as simple as it appears I have found. I also have realized that it is really difficult to gage what other kids are doing. That is, just because I don't see a kid with a Harry Potter book in his hand, doesn't mean that he is not reading it at home.
While many of the early bloomers are indeed gifted and will continue to be so, some of them have been completely turned off by a lack of challenge in school. There are others who were "hothoused" in the earlier years, evening out as other catch up in reading or math.
Then there are some like your kids who had other interests in preschool and were not early readers for example. Looking back, can you tell that they were smart? For instance, my girls were by no means early on the academics (although my oldest did start reading at 4, she had NO interest in letters before that, she did not count to 100 early on, etc.); but I was aware that they were very smart from the things they said, their complex pretend play, etc.
What is the deal with your gifted program? I would not take a "no" that easily. How do they identify gifted students? How are spaces allocated? I can see them turning him down for this year, but I have a harder time understanding that they would be no space for him ever. Can you talk to the gifted coordinator for your district? Check online to see their policies or ask for those in written format.
There are those who are late bloomers. Our dds are in a gifted school and I have heard of parents enrolling one of their children but not another, then suddenly, the other one starts to take off academically, and they realize that s/he was gifted as well.
