The Lycanthropic regeneration should give him back his voice and his hearing. It is probably responsible for his aura of command. He is now an Alpha beast and has the confidence knowing that he can take on any physical threat and most social ones.
He may not be speaking because he does not have to. He may have a more animalistic view of speaking, i.e. communicate only when there is something truly important to say. Day to day chatter has no place for him.
Because of intrigues at his court, he is possibly keeping the fact he can now hear (and speak) a secret. He is also keeping his lycanthrope a secret. Someone, a trusted advisor of his father probably, knows the truth and is helping him keep it a secret and hushing things up.
By the time it becomes apparent that he is not a deaf mute, he will have a treasure trove of secrets to work with. People will talk around him, thinking he can not hear them. With his superhuman senses, he will have a commanding knowledge of what is going on around him and in the entire castle. His skill at controling his morphic abilities will probably mature about the same time. This means he can deal with certain forces, as needed, without tarnishing the Crown. (Gasp.. he was torn apart by a beast unknown? We shall hunt for this beast. (and of course fail in finding it.))
This will make him a formitable king when dealing with his own court and outside forces. His secret advantages will give him edges. As long as everything except the lycanthrope is revealed, he will just seem as a knowledgable and wise king. Go to Comment
Capn, I think it's meant: If someone catches him as a child thinking he will be worth a pretty penny with ransom, and locks such a weak child in a small, wooden cage, Won't they be surprised when the boy changes form and bursts out of it?
I like the idea, especially Moons additions to the idea. Perhaps he is still mute simply because he regained his use of vocal chords too late (perhaps not) and so cannot talk without calling attention to his state.