So e.g. northern Ireland seceding would suffice to settle this as "yes", right?

@ShakedKoplewitz yes

Does this question imply a sole monarch? Wouldn't Kate be queen if Will becomes king?

@NickAllen no, she's "duchess consort" (like Charles' current wife).

@ShakedKoplewitz Looks like Camilla is "Queen Consort", which doesn't really meet the intent of this question and doesn't resolve it, but it also looks like she might be considering just changing her title to "Queen". Would that resolve it?

The intent of the question seems to be whether there's a solo queen with a "prince consort" or something, but that's not clearly established.

https://www.independent.co.uk/life-style/royal-family/camilla-title-queen-consort-coronation-b2290287.html

@ShakedKoplewitz on reexamining the question it doesn't look like there's any grounds for saying it doesn't resolve "no" if Camilla's official title becomes "Queen"; at most it's just not the way @MartinRandall envisioned.

@NickAllen Yes, the description specifies "female monarch", and a title of "queen consort" would not satisfy that. I'll update the description to make that explicit.

@NickAllen I haven't specified the result if there is a power sharing agreement between a king and queen. Let me know if that impacts your betting.

@MartinRandall the lack of clarity here definitely does impact my betting. I think the chances of someone having the title "queen" (not "queen consort") by virtue of being married to a king within the next ten years is extremely high; if not Camilla then Kate. If that wouldn't resolve the question as "no", and if the question is only wondering whether there will be another solo female monarch with at most a "prince consort" then my estimate will be much lower.

@NickAllen If there's a power sharing agreement, how would I determine whether enough power is being shared to make the queen a monarch?

@MartinRandall I don't know if there's any particular power implied in being queen. Can't help you there. Was a certain power level the intent of the question?

@NickAllen I think if Camilla and Charles become joint Queen and King then when Charles dies Camilla will be solo Queen (and not just Queen Dowager) so maybe it's not as big a difference.

@NickAllen Clarified that she doesn't have to be a solo queen but does have to be queen suo jure.

This being false is contingent on AGI and immortality both failing to happen by the time the entire currently living chain of succession dies (possibly longer if the next heirs are also men) and the UK lasting as a country that long and not becoming a republic. That's three separate ways this could fail, at least two of which seems ~50% likely to happen in the next century. 40% is undervalued.

(Otoh, if in the glorious transhumanist future the immortal god-king William decides to try out changing bodies for an afternoon, does that count as yes?)

@ShakedKoplewitz I'm not going to attempt an advance definition of "female" in the glorious transhumanist future. So I'll commit to not betting. 40% does seem low.

@ShakedKoplewitz what if Prince George comes out as trans

@ShakedKoplewitz it's not outright impossible that the UK survives AGI, and immortality won't necessarily mean Charles III will reign forever (it might become customary to abdicate on one's 100th birthday for instance)