We're told that a Canon EF 200-600 f/4.5-5.6 IS development is on schedule and that the lens will be released some time in 2016.
The source didn't know if it was going to be an L lens or not, but assumed that it wasn't going to be. The lens would likely be priced below the EF 100-400mm f/4.5-5.6L IS II, and compete directly with the Sigma and Tamron supertelephoto zoom lenses.
It makes sense to us that it would come below the EF 100-400mm f/4.5-5.6L IS II as far as price point and quality are concerned. We're confident such a lens from Canon would still have terrific optical performance and a relatively light weight.