In general I have always believed Canon (and most other manufacturers) have a hole in their lineup in terms of high quality telephotos. On the one side you have their 'budget' telephotos like the 400/5.6 and the 100-400 and on the other side you have their high end telephotos beginning with the 300/2.8 II. The problem is there's really nothing in between unless you buy used. So you either pay ~$1700 for the current 100-400 or you save up $7k for the 300/2.8 II (or more likely $10k and up for the 200-400 or 500/4).
I agree there's a gap, but it's been there long enough for Canon to have filled it, if they wanted to.
Very true, but that doesn't mean I can still wish they filled it.
Then again from Canon's point of view:
- I purchased the 100-400
- I purchased the 70-200/2.8 II + 2x III. The image quality + AF was close enough to the 100-400 to no longer justify carrying it.
- I still wasn't happy with the image quality + AF, so I bought the 400/5.6
- I still wanted something with IS and a bit more reach, so after some time I used the money I was saving for the 600/4 II and bought a 200-400/1.4x with the justification that it is far more flexible.
So in the end Canon got a lot more money out of me than if they had just introduced a 500/5.6 IS in the first place.