TESO has been surprisingly little hyped so far, almost less than WoW was back in the day. It won't kill WoW, no. Why would it want to anyway? That would mean more of that casual lobby-game design that I and many other players absolutely hates. If it becomes a success with millions of players then good, but it won't be because it killed WoW, it would be because it was so true to TES that most TES players play TESO as well.