No MMORPG will dethrone WoW as the ruler of MMORPG's. World of Warcrap is to MMORPG's as the Wii is to video game platforms. Making your game different is going to make it successful but it will never be as successful as the clear ruler, and trying to copy it is just going to ruin it because everyone already owns the one that's been out for a long time.
WoW was marketed to the right people, as was the Wii.
WoW is easily played by anyone of all ages, as is the Wii.
WoW is cheap to get into (you don't need a $5000 computer to play it), and the Wii is the cheapest of the 3 current-gen platforms.
WoW has perfected its gimmick over time, and other games trying to copy it will automatically fail; the Wii has perfected its gimmick and other platforms trying to copy it will automatically fail.
WoW has ass-tastic graphics, as does the Wii.
Y'know, I could just go on with this list. But my point is, dethroning WoW's audience is like trying to dethrone the Wii's audience. It just isn't going to happen.