I can think of a perfect example. Lets take The Earl of Wessex and the plan that, in time, he will be created The Duke of Edinburgh. Now, things have to happen before this can occur. 1.) Both HM, The Queen and the present Duke of Edinburgh have to pass away. 2.) When Charles becomes King, all his previous titles, styles and whatever revert to the Crown including the title of Duke of Edinburgh (which he would inherit if his father dies before his mother). He is no longer The Prince Charles, The Duke of Cornwall or the Prince of Wales or any of his previous titles and styles that he now holds. It is Charles' prerogative as the monarch then to created The Duke of Edinburgh title for Edward.
Now all this has been done. Charles decides to abdicate and retire with Camilla to the far reaches of Antarctica to raise Emperor penguins. All his titles and styles he held as King (Duke of Lancaster etc) are inherited by William leaving Charles without anything. It would be up to William to decide just what his father's titles and styles would be. Could be anything William chooses.
The kicker is that when Edward VIII became King, all his princely titles reverted to the Crown. He only held those that a King would have.
At least this is how I understand it.
'When Charles becomes King, all his previous titles, styles and whatever revert to the Crown'
What are your authorities for this? It is true that peerages merge with the Crown, though not the Dukedom of Rothesay for instance (which is a feudal title, not a personal peerage). But I know of nothing which says that all titles, styles and so on will merge with the Crown. More importantly, the Letters Patent of 1864 say that the HRH title will be borne 'at all times'. There is nothing here which says that a person ceases to be an HRH when he succeeds to the throne. The title might be submerged but it is not subsumed. So, we have specific words which say that a person will be an HRH 'at all times'.