Years will eventually pass and Blizzard will keep creating content. However someday the game will eventually just not be profitable enough and they'll just have to discontinue World of Warcraft. Could be a few years or even a whole another decade, who knows? You'll have your moments shared with guildies and retards, screenshots and videos, unfinished legendary questlines (these would bug me forever), unobtained mounts despite months of farming, achievements left unaccomplished and overrall happy memories along with annoying and funny ones too :P. But that's beside the point. When it does end and if you are still playing, what would you do? Would you start to connect to a private server? Go into depression? (Sadly enough I used to know someone that actually would have) Just continue playing any other games you play as if nothing happened? Spend even more time on these games? Spend more time offline? So the main question is:
What will you do when World of Warcraft comes to an end?
Personally I think I'd try out Everquest (or Evergrind as apparently it's reputation precedes it) or actually progress further with some other random games.