Given the high ISO capabilities of this camera will this change the need to use the heavier glass? I'm specifically thinking of the 300 2.8/500 4.0/ 600 4.0. Other than the OOF background, which most times can be achieved in PS what is the gain if you can dial up the ISO to attain a shutter speed of 1000+? What does this do for IS/VR/HSM technology? Will it be needed?

