Dumb question: would the UK no longer be the UK at that point?
Today, Wales is thought of as a constituent country of the United Kingdom, on par with England, Scotland, and Northern Ireland. From a standpoint of the monarchy, it's all one unified realm of The Crown.
FWIW, the Tories probably going to be in power for at least another half-decade or two.
2) The queen has now reigned for 68 years
2) It's still a kingdom, whether a king or queen rules.