Wives of Kings of England(and Britain) have always been called "Queen Consort",they are not Queens in their own right but only by marriage to a King.They cannot rule after their husbands die,but continue as Dowager Queens,their son(or the next in line of sucession) comes to the throne as King.
The last (possible) male who had a claim by marrying a reigning Queen,Phillip of Spain with Mary Tudor,could (technically) have asserted a right to the throne of England after Mary died but did not (even though he sent the Armada against her sister),
William III & Mary were joint monarchs(and therefore equal) and they were cousins,
They were asked by parliament to suceed James II(Mary's Father).Mary died first,and William ruled on,but even if he had died first(in this case only) Mary would have still be(reigning) Queen.
After this joint couple,it looks like all male husbands of reigning monarchs were as follows:~
Queen Anne had a husband(Prince George of Denmark) who was known just as Prince George.
Queen Victoria's husband was Just Prince Albert,but was promoted to the title of Prince Consort.
QE2 husband is Prince Phillip,Duke of Edinburgh.
So to conclude when Charles becomes King Camilla will constitutionally become Queen,whatever he decides to call her.