Really I am impressed with the number of people who are giving WoW such credit. I guess as it relates to the OP No ToR will not "kill" WoW, much like Wow didnt kill Everquest. Truthfully as long as there are Koreans, World of Warcraft will never die.
But let us be realistic, The impact ToR has on WoW WILL LIKELY be similar to the Impact WoW had on EQ. This is obviously provided that ToR is good and actually delivers on the promises Bioware has been making. The reason is that if the Story pillar plays out the way Bioware has been hyping it, It will be a keystone convention for MMOs across the board that basically will practically become prerequisite for new MMOs to have in order to compete.
WoW will in turn have to compete with that and due to the limitations of the engine, unless they basically plan to completely recode and rebuild the game from practically the ground up it will always be lagging behind the curve.
And when presented with a game that has all the same polish and features WoW has, Plus has an added dynamic that WoW doesnt, people will find it harder to go back to WoW long term after the novelty of the new next big thing wears off.
Lets be honest (at least more honest than blizzard is about their subscription numbers) You will see an initial dropoff in WoW subscriptions after ToR for the first 1-3 months. In that time, the novelty will wear off for the bleeding edgers. There will then be a return influx to WoW. Even with an insane overestimate, just for argument sake say ToR eats away at 50% of WoWs subscription base, ANY MMO with 5 million subscribers is extremely sucessful because for most MMOs, they can exist fairly comfortable with a subscription base of 200,000 or more.
So is anything going to kill WoW? Only Blizzard will do that. Is ToR going to take a large bite out of the WoW subscription base? Not really considering that the star wars fanbase will likely be tied to the more English speaking markets, and the bulk of WoWs subscriptions are still based in the Asian markets. Will ToR take a large bite out of the profits that Blizzard sees from the US.. You better believe it will.
Fact is WoW will be around for many years to come. Just look at the case example of Everquest. In its heyday, it had half a million subs. In the 6 plus years since its heyday its population has been cut down to 2/5ths what it once was, yet it is still trudging along. Even if WoW does start to take a downturn, its going to still be seen as profitable for many years to come. It simply wont die, but it will get wounded from ToR, and perhaps DCUO for the ENG market, and a few other upcoming MMOs will help to further chip away at the immovable object.