Canon Rumors recently got word that a new EF 100-400 f/4-5.6L IS lens could be announced around Photokina 2012.  The current 100-400mm model is getting a little long in tooth and is known as a dust sucker thanks to the push-pull zoom barrel.

The new model is rumored to carry an f/4-5.6 range - instead of the current f/4.5-5.6 aperture range.  Additional rumors have included the possibility of a twist-zoom barrel instead of the current push-pull design.