Sigma 500mm f/4 DG OS HSM lens rumored to be announced next week at Photokina

Sigma is rumored to announce a new 500mm f/4 DG OS HSM flagship Sports lens at the Photokina show next week. Here are the specifications:

WEIGHT: 3310 gm (7.3 lb). This is only 220 gm (about 0.5 lb) heavier than Nikon’s “new” 500mm f4E (fluorite) lens.
LENGTH: 380.3mm (15″). This is very slightly shorter (7 mm) than Nikon’s “new” 500mm f4E (fluorite) lens.
COUNTRY OF CONSTRUCTION: Japan
MATERIALS: Magnesium alloy barrel, carbon fiber hood, brass bayonet mount.
OPTICS: 16 elements in 11 groups, including 2 FLD (presumably fluoride?) elements and one SLD element.
NUMBER OF DIAPHRAGM BLADES: 9.
ENVIRONMENTAL SEALING: Dust and Splash-proof construction.
ELECTROMAGNETIC DIAPHRAGM: Yes (Nikon version only).
OPTICAL STABILIZATION: 4-stops; 2 modes (mode 1 for general photography; mode 2 for panning).
CUSTOMIZATION & FIRMWARE UPDATES: Via USB dock.
OTHER: Tripod collar with 90 degree click stops (that can be turned off); optional teleconverters, mount converters, drop-in polarizer, and USB dock available.