We self referred both our kids for speech therapy when they were almost 5 and 4, Craig because he couldn't say his "r's" and Ciar because he had problems with "k" and "g". Apparantly some kids don't get the "r " sound until they are 6 or 7, so although they said they would take the referral - they probably wouldn't do anything until he was older, we waited about 6 months for an appointment and by that time he was fine. Ciar was still having problems, so he went along for his first appointment - they gave a couple of techniques to try and he didn't even need a follow up appointment. We were concerned because the sounds they couldn't pronounce were in their own names and we knew that Craig's teachers surname started with an R. He called himself Cwaig.
My sisters little boy goes to speech therapy not because he has sound issues so much as he had very delayed speech and he has trouble processing speech. He understands all language, and can individually make all sounds, but he has trouble forming clear speech all the time - it also affects the way that he learns to read - he is 5, so i guess what I am saying is that it depends on why they feel he would benefit from speech therapy, does he have problems communicating, or is he having trouble with particular sounds?