I believe Canon can lower the price of the 5Diii when the 5Dii is officially discontinued. It is actually smart of them keeping the 5Diii high- it keeps the "old" 5Dii selling really well as a "value" camera at 2k!
Nikon discontinued their D700 and needed to be aggressive to compete with Canon's market dominance.
What is wrong with Canon's sensors? To be honest, I never really think about the sensors in my digital cameras anymore- they are all good. I care more about the user experience of the camera, and to me, Canon cameras feel better. Nikons have a ton of weird buttons & dials and other things I don't care for. Oh & I like Canon glass.