I have loaded an MTF chart comparison onto the Canon EF 100-400mm f/4.5-5.6L IS II USM Lens Review page. Compare the 100-400 L II's MTF charts to those of the 100-400 L, 70-300 L and 400 f/5.6 L. With-extender charts for the new lens are included.
Again, B&H is accepting Canon EF 100-400mm f/4.5-5.6L IS II USM Lens preorders and I recommend preordering early if you want this lens anytime soon. Adorama and Amazon are also accepting preorders.