I have received various bits of info over the last few months about Canon's plans in the 400mm range. There is lots of desire for a new 400 f/5.6L and 100-400, and both may finally be getting an update. It feels like the 100-400 has been in the update cycle forever, but judging by how many of these things Canon sells, I can see why they've been in no rush to have it replaced.
Below are lenses that are apparently in prototype form and are on tap to be announced in 2013.
- EF 400 f/5.6L IS (Highly desired)
- EF 400 f/4L IS (Not DO)
- EF 100-400 f/4-5.6L IS (Not push-pull & patents exists)
- EF 200-400 f/4L IS 1.4x (Long known about)
There seems to be a theme developing with Canon offering more options in the same focal length range. Best guess pricing will also have a pretty wide range, from a $2000 400 f/5.6L IS up to the $11,000 EF 200-400 f/4L IS 1.4x.