Thunderfury, Blessed Blade of the Windseeker will receive a nice change. It will no longer be a mainhand only weapon and you will be able to wield it in offhand. The change has been confirmed on the US Public Test Realm Forum.
Personally I do not understand the hype about this change since the sword is rather rare and there is quite a number of guilds out there that have not gotten the necessary drops in 1 year of weekly Molten Core raids.