Princess Robijn said:Will Lady Louise when she becomes of age, be able to choose to be called HRH Princess Louise of Wessex?? (Princess of the United Kingdom of Great-Britain and Northern Ireland)
Technically, yes. But it remains to be seen whether the decision to style Louise a daughter of an Earl is the first step towards a formal downsizing of family members who are entitled to be prince/princess of the UK with the rank of Royal Highness.
My prediction is new letters patent will be issued which will result in the loss of the titular dignity and rank for Eugenie and Beatrice, and probably Harry as well once William has his first child. They would then retain their royal peerages without royal rank.