OP, I would not be worried--this is extremely common, as many posters have said.
Switch them from diapers to GoodNites--more expensive but much less demeaning.
I had one son that wore GoodNites (soaked every morning) until close to his 10th birthday and another that wore them until age 6 1/2. They both started waking up dry without any intervention, pretty much from one day to the next. After they woke up dry for 2 weeks straight they started sleeping in underwear and B"H never wet the bed again.
