Cata to wipe out half player base?

Now hear me out. I love WoW as much as everyone here but I have a very odd feeling that half the players are going to be gone once Cata comes out.

NCP's are going to die because the world is being basically ripped open yet all the player characters are going to survive. Which is a little unrealistic. How about this. RNG chooses random characters and just deletes them, as if they have died. Never to be recovered? That way WoW becomes more realistic, we fill up the game world with people relevelling their characters because they have "died" etc.