I should never exaggerate the importance of patent publishing (some of them are only a way to make sure nobody can re-use the same idea when invented independently), but it is interesting to notice that Canon published a patent for an architecture targeting a 100-400mm f/4-5.6 tele-zoom which could well become the next replacement for the current 100-400mm.
Canon patent: 100-400mm f/4-5.6
Current Canon 100-400mm f/5.6
So, patience is still very necessary here (Canon is finishing the actual launch of its pro primes lenses) but early 2012…
Source: Egami, an excellent technology patent blog.