His title of “Duke of Edinburgh” will now pass to his youngest son Prince Edward and it will be in very safe hands. RIP Philip.
Actually, Prince Phillip’s title of Duke of Edinburgh has passed to Prince Charles as heir to his father’s titles (due to the way the third incarnation of the title was created under Letters Patent by his late father-in-law, King George VI when Prince Phillip married the then Princess Elizabeth).
Only when Prince Charles accedes to the throne as King will the current incarnation of the title be returned to the Crown, and the fourth incarnation of the title created to be passed to Prince Edward (the current Earl of Wessex).
However, if for some reason Prince Charles does not accede to the throne as King (for example if he dies before the current Queen), then the title Duke of Edinburgh would pass to Prince William as Heir to Prince Charles’s titles.
Only once Prince William accedes to the throne would the title be returned to the Crown and the fourth incarnation of the title be passed to Prince Edward.
If for some reason Prince William doesn’t accede to the throne (for example, he dies before both HM Queen relinquishes the throne or dies and Prince Charles doesn’t accede to the throne as King because he dies before the current Queen), then it would pass to Prince George (until his accession to the throne when again the title Duke of Edinburgh would pass to the Crown for the fourth incarnation to take place.
And so on!