That's what Canon Rumors has been told, that we can expect up to four new lenses in the 400mm range. Quoting:
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)