You can't really "kill" an MMO, but you can become the new big boy. Honestly no game will seriously compete with WoW until it both has a quality design team with a free hand, and a budget at least equal to the one WoW was developed on for the current economy/value of currency.
Fly by night MMOs aren't going to be able to do it. Games like "Age Of Conan" had the potential but did not have the budget, development time, or perhaps the people to do it. Age Of Conan was a mere shadow of what it was supposed to be when planned initially.
Warhammer was doomed from the beginning for similar reasons to Age Of Conan, combined with a lack of planning. They should have seen how things were going to turn out when the interest in "Destruction" turned out so high both in forums and through the "Road To WAR" promotion. Without balanced sides I think they got themselves nuked right at the starting line.
Knights Of The Old Republic has the potential to be the next big one, BUT it's making similar mistakes. Right now the game seems to be afflicted with "Sith Mania", and that goes for the design team/game concept as well. As a result I think more time and effort is being put into the bad guys and making them "soooper awesome". So in the end your going to see a bajillion people playing Sith compared to Jedi, and the Sith having been made a lot cooler/better performance wise, despite the fact that the Sith are supposed to be on the verge of getting WTFpwned so hard that a few thousand years later nobody will even know what a Sith was for sure.
I also do not know what their budget is, but they DO have Bioware who are talented developers like Blizzard. I think they are simply suffering from lack of foresight in design.
DC Heroes and Champions Online are coming out also, but I think super-hero MMOs are definatly a niche market and aren't even intended to play at the WoW-level.
>>>----Therumancer--->