Apparently both of the new teleconverters are delayed as well.
EF 300mm f/2.8L IS II USM, EF 400mm f/2.8L IS II USM and EF 8-15mm f/4L Fisheye USM lenses delayed
Following the announcement of the new EF 300mm f/2.8L IS II USM, EF 400mm f/2.8L IS II USM and EF 8-15mm f/4L Fisheye USM, on 26th August 2010, Canon has now delayed the introduction of these lenses due to some adjustments in the manufacturing process. These lenses are now due to be released in March 2011.
Canon would like to apologise to any customers who will be inconvenienced by these delays.