Suppose one night William, Prince of Wales and his wife and kids get some bad romaine lettuce in their Caesar salad and everyone keels over dead. It could happen.
That places the new Duke of Sussex, aka Henry, aka Prince Harry, aka Mr. Meghan Markle, third in line for the throne, after his grandmother, Elizabeth II, and his father, who presumably will be Charles III. Voila, Harry eventually becomes King Henry IX, unless he picks a different regnal name.
So if that happens, will Meghan Markle be properly Queen Meghan? My understanding is that Camilla will remain the Duchess of Cambridge, not Queen Camilla, when her husband becomes King; is Markle in the same boat, stuck at Duchess of Sussex no matter what?