My grandson was over three before he really started talking and at five is quite advanced. We have been amazed what he took in ans he still has days when he is not talkative. He had a bit of speech therapy and is not going to school next year but that's not a problem as another year at kinder will not be bad for him.
Keep reading and talking to him as he will be taking in everything you say.
I love ringing him and having a conversation with him which is getting clearer all the time. When you ring your Mum put the phone on speaker and get her to say hello and ask how he is.
I have heard many stories about kids not talking to go on to be chatterboxes. Some kids just don't want to talk unless they want to.