New rumors from Canon Rumors suggest that Canon will release a replacement to the aging EF 100-400mm f/4.5-5.6L IS lens next month.
The new 100-400mm lens is rumored to be similar in design to the recent EF 70-300mm f/4-5.6L IS lens, which offers a thinner focus ring near the base and a wider zoom ring near the front of the lens.
Additionally, the lens hood is rumored to feature a retractable opening that will allow you to adjust your circular polarizer or fader ND filter while keeping the lens hood on the lens.