Duke and Duchess of Cambridge?

[Chas]

I have some questions for all those with a more developed knowledge of titular protocol. Everyone's been throwing Princess Kate around, but I started thinking about it and just didn't think it played out like that. Wanted some answers.

1. What is Catherine Middleton's last name now? Windsor? Wales?
2. Is she a Princess? Based on my own limited knowledge of how it works she would be Duchess of Cambridge as Prince William's prince doesn't come from a title like Prince of Wales but from his blood relation to the Queen. So they are Prince William, Duke of York and Duchess Catherine of York? She wouldn't become a princess until Charles becomes king and William becomes The Prince of Wales, right?
3. If they have a son before Charles becomes king would he use the Prince's second title as Earl of Strathearn or does he just use the royal Prince title?

Any info is appreciated.

1. She no longer has a surname, but if one is required (commercial flights and the like) then she can use Windsor.

2. Yes, she is a princess, because she married a prince. She is not a princess in her own right as she was not born a princess, therefore she is not and never will be Princess Catherine (or Kate). She is officially Her Royal Highness Princess William Arthur Philip Louis, Duchess of Cambridge, Countess of Strathearn, Baroness Carrickfergus.

3. The first son of their marriage would be His Royal Highness Prince firstname of Cambridge Earl of Strathearn.

Regards

Chas