I have wondered from the start given his age etc. Why they haven't just gone straight to William
To miss out Charles and go straight to William would have required Parliamentary legislation while the Queen was still alive, which she would have had to give the Royal Assent to. Can't imagine that she, or Charles, or William, would have wanted that, or that any PM would have had the nerve to suggest it.
I should think William and Catherine are hoping that they won't have to take on the job until their children are quite a bit older.