what if The Queen Elizabeth II outlives Prince Charles, Prince william, and Prince George?

Then the next in line would take the crown.

Princess Charlotte will become Queen on her abdication/death.

https://en.wikipedia.org/wiki/Succession_to_the_Br...

They change uniforms and dance - does it matter.

The chances of that are very slightly above zero.

Princess Charlotte would become Queen, after her is Prince Louis, her younger brother,

Then sixth in line is Prince Harry, Duke of Sussex, the younger son of the Prince of Wales, followed by the child his wife is expecting.

And so it goes on with the remaining three children of the Queen and their children.

Charlotte becomes heiress apparent. The Queen will then change the rules about the titles Prince/ss of Wales, Duke/Duchess of Rothesay and Duke/Duchess of Cornwall and their respective subsidiariy titles to allow for female heirs to hold such titles in their own right.

The Queen will also change the entitlement to automatic acquisition of the HRH by female lines of descent. Prince Louis future children will never have automatic rights to royal status at birth.

Next in line would be Princess Charlotte, then Prince Louis, then Prince Harry. If Princess Charlotte became Queen, a regent would be appointed 'til she reached adulthood.

Then when she dies, Princess Charlotte becomes queen.

Then Charlotte would be next in line, Louis after her, Harry after him, etc.

Then she stays being queen (unless she abdicates).