I remember reading an analysis of royal experts saying that rewriting the 1017 letters of patent created a difficult situation. If new letters of patent were issued to redefine who are HRH Prince/Princess by restricting it to the children of the monarch, family of the heir, the moment new letters are issues the following people would lose their HRH Prince/Princess overnight
Princess Beatrice, Princess Eugenie, James Viscount Severn (rights), Lady Louise Windsor (rights), Prince Richard, Duke of Gloucester, Prince Edward, Duke of Kent, Prince Michael of Kent, Princess Alexander, Future children of Harry (rights).
It is thought this is the reason nothing was formally acted when the situation with Edward children arose, mainly because of the impact on the people listed above.
I truly think Charles once monarch won't do anything about it.
The Queen's cousins are old, and moving toward retirement, and their issues are not HRH
Beatrice, Eugenie, and Louise issues won't be HRH
potential HRH once Charles becomes King are not that many
HRH Princess Royal
HRH The Duke of York (assuming he does not remarry, if he does, HRH the Duchess of York)
HRH Princess Beatrice, Mrs xxx
HRH Princess Eugenie, Mrs xxx
HRH The Duke of Edinburgh (Prince Edward after the death of Prince Philip)
HRH The Duchess of Edinburgh
HRH Prince James of Edinburgh (and potential wife)
HRH Princess Louise, Mrs xxx
HRH The Prince of Wales
HRH The Princess of Wales
HRH Prince George of Wales
HRH Princess Charlotte, Mrs xxx
HRH Prince Louis of Wales
HRH The Duke of Sussex
HRH The Duchess of Sussex
HRH potential children of The Duke of Sussex
At the end of the day I think it is Harry who will decide if his children are HRH or not, He has a great relationship with his Pa, and Charles won't do anything Harry does not want