There is a real possibility that the UK of GB & NI will cease to exist, being replaced by the separate Kingdoms of England (including Wales) and Scotland. If the break-up happens while the present Queen is alive, a personal union of the two crowns would most probably be agreed upon but if Scotland becomes independent near the start of a new reign, that may not be the case. I wonder in that case if the Scots would opt for a separate King/Queen of Scots (maybe even someone from the BRF, such as The Princess Royal, as Queen Anne II, for example), continued personal union with the English crown under Charles III, or a republic.