DD did the same thing about talking a little later than typical kids, but interestingly since then her enunciation has always been excellent--we had very little 'baby talk.' She also did the echolalia thing especially when she was 2-3, and would repeat the whole thing that was said to her, without changing the pronoun. She stopped that but now she does the palilalia (?) thing--repeating her words under her breath. I think she's just fine but you should be aware the echolalia is sometimes associated with the autism spectrum, and our DD has been diagnosed as having Asperger's/ high functioning autism. But IMO I wouldn't worry about your DS at this point if that's the only unusual thing you've noticed; as you say, he might just be processing how to communicate.
