Cannon has announced its new generation 500 mm f/4L EF IS II USM lens.

The major highlights and innovations on this lens are:

A revolutionary composition of magnesium and titanium construction elements have had a significant impact on the weight of this beast by almost 1.5 lbs.

Added to it are completly redesigned fluortie optics which enhances image sharpness considerably.

A three stage Image Stabillization allows nearly a 4 stop slower shoot mode

Power Focus mode allows smooth focus change when shooting video

It currently retails at around 10,500 USD

more details on Canon's site:

Canon U.S.A. : Consumer & Home Office : EF 500mm f/4L IS II USM

regards
Rajan