The EF 100-400mm f/4-5.6L IS lens will be coming to an end soon. And the replacement for this lens has rumored for a long time. It is said new EF 100-400mm f/4-5.6L IS II will be announced in late 2013 to early 2014.
We are also told until the EF 200-400mm f/4L IS 1.4x production reaches demand, Canon will not be producing this new 100-400mm lens.
via: Canon Rumors