[coldtea]

>When Queen Elizabeth died it would have been “the queen is dead, long live the king”, as the dead thing is the predecessor and the living thing is the one that follows it

And if a freshly dead king is replaced by a new king, it's "the king is dead, long live the king".

The predecessor and the living thing doesn't have to be of the opposite sex, or use a different term:

https://en.wikipedia.org/wiki/The_king_is_dead,_long_live_th...!

It's a very famous idiom.