So I was reading the Royal lives clause page on Wikipedia and noticed that on the sample clause there, it states "...21 years from the death of the last survivor of all the lineal descendants of [his late Majesty King George V or some other British monarch] who have been born on the date of this agreement."
The RCID King Charles III clause didn't have that. Instead, it says: "...until twenty one (21) years after the death of the last survivor of the descendants of King Charles III, King of England living as of the date of this Declaration." While I know it's a just sample and probably isn't used in legal practice, it's interesting that the clause didn't include similar wordage as the sample one. I'm no attorney/lawyer, but to me, this implies that the coverage of the clause not only spans the lifetimes of those in the recognized lineal line (William, Harry, George, Charlotte, Louis, Archie, and Lilibet) but also the ones outside the line (assuming that Charles III had secret illegitimate children who then had descendants of their own, albeit just unrecognized by the Royal Family because "dirty laundry").
If somehow the lineal line died out (either through wars, accidents, illness, ) and if there are people outside the lineal line who call Charles III a direct ascendant with valid proof (DNA testing, NDAs from RF, etc.), the clause will still hold. Knowing how protective RF is of their dirty laundry, CFTOD would have to move heaven and earth to find all unrecognized descendants and uh, liquidate them, just to gain full control of the property.
Clever move, Disney. Clever move.
(Now, I'm not saying that Charles III actually has illegitimate children, but wouldn't it be wild if he did...)