An announcement of Canon EF 100-400mm f/4-5.6L IS II lens is coming soon, said CR.
After EF 24-70 f/2.8L has been redone, the most requested lens to be replaced with a new version is the Canon EF 100-400 f/4.5-5.6L IS. So the new 100-400 II should be ready in 2012. There is also a new patent for new 100-400mm:
We expect EF 100-400mm f/4-5.6L IS II coming before Photokina 2012.