Or maybe, they will combine WOW with the Warcraft RTS ... and have WOW players able to invade RTS games at any time (other than campaign) as individual units.
And then, if your character dies in the RTS world, its permanently trapped until the RTS player says different. Usually this will require allowing the RTS player to use your character as a unit in his game.
Then you will be free to continue playing that character in MMOs and he can use your unit in his RTS games. The one caveat, however, is that if you re-enter an RTS game where he is playing, if you attack one of his units you automatically die again. You can pay him with your WOW gold, which is converted to RTS resources to the player (which may be a reason to let you be able to return to WOW). If you don't have any WOW gold, however, you can either become his unit in the game, acting independently not requiring food, and fighting against the other units from a 1st player perspective ... or you can lose that character forever and create a new WOW character.