Latest rumor has it the AMG version will NOT be getting a Supercharged V6, instead, it'll be getting the old 24-valve 5.5L V8 that's currently in the CLK55 and the ML55, not the supercharged version in the S/SL/CL/E55. Motor makes 362hp/376tq. This was mentioned by the guys in the AMG club (and employees) in germany a few months ago and confirmed in Bild.
The car's also getting the AirMatic adjustable suspension, Active Body Control, and SBC Sensotronic Brake control. Bye bye 3200lb curb weight!
Engine choices should be the 1.8L Supercharged 4 banger (~200hp), the new 3.5L V6 (~250hp) and the AMG 5.5L V8 (362hp).
Here's some pics, which looks very close to the black disguised car that's been running around in the States.