No info yet
No favorite names yet.
John may not be chosen due to King John and the two princes who died young (sons of Edward VII and George V). Also, both Prince Alberts that became king did not use the name, and Prince Albert Victor died young, so Albert seems "doomed" as regnal name.
If William and Catherine are going to be very traditional, I think they will choose George for a boy. If not, I'd be happy to see Arthur, Frederick, or Edmund.
It's harder to guess a girl's name. I'd be happy to see Alexandra, Matilda, Caroline, Eleanor, or Alice. I also think Georgiana is a good possibility. Spain will have a Queen Leonor, but I don't know if that would influence them to not choose Eleanor.