The value of art isn’t that it exists.
The solution to WoW ending is simple: When it goes under, be the highest bidder on the remains. That is, of course, if they end up selling either everything or just the rights to keep it going. Turning WoW into a single player game would be more like destroying the spirit of WoW, far more than pulling the plug and only finding it on pirating sites.
For me? If WoW were to disappear, just means time shifts to a different hobby because everything passes eventually, no point mourning what is gone or dreading that it will someday disappear, just enjoy what is there while you have it. Or don’t, that’s up to you.