Will it take the 1.4x or 2x extenders?
If it would take a 1.4x AND they'd release a high-pixel-density 1.6-crop body (i.e. 7D Mark II) that could focus at f/8, Canon might get several thousand of my dollars.
Agreed. 21-24 mpx 1.6 crop, 8 fps 7D2 paired with this lens would make a great kit.
In times past, I spurned the 100-400 in favour of a 300 f4; perhaps, I may look to this in the future. I now have a 300 2.8, which I use extensively, but a 100-400 would be nice for a second camera...