It's actually quite sweet.

Kate Middleton could receive a new title when Prince Charles becomes King - and there's a very sweet meaning behind it. When she wed Prince William in 2011, the pair became the Duke and Duchess of Cambridge. And when Prince Charles inherits the throne, the Duke and Duchess will move up the line of succession - and, in turn, receive new titles. For Charles, who is the Queen's eldest son, to ascend to the throne, he would have to vacate the Prince of Wales title. The title is given to the heir apparent to the throne which, in this case, means that Prince William would become the new Prince of Wales. This means that Kate's title would also reflect the change, and she would be offered the title of Princess of Wales - the same title William's mum, Princess Diana, held. Even though Charles is the current Prince of Wales, his wife, Camilla, chose not to use the title when they wed in 2005. It has been speculated that her decision was made out of respect for Diana. Instead, she uses the title the Duchess of Cornwall - the feminine equivalent of Charles' Duke of Cornwall title. This means that if Kate decides to use the title, she would become the first person hold the Princess of Wales title since Williams's mum.