The car that authored the "four-door-coupe" terminology – and a great deal of Internet debate and dictionary definition checking – will introduce its second act toward the end of 2011. Unsurprisingly, the new model (which is expected to wear a 2011 designation), will look much like the current model. That's the way it goes with genre-defining things most of the time.

Perhaps it is just our eyes, but in the spy shots it looks like the car's rump could be even more sleek, with the glasshouse landing even further toward the rear of the car. Also, the mirror mountings have changed – at least on this prototype – from the A-pillar notch to the doors. In line with Merc's current designs, they are now giant square flaps mounted on stalks.

Engines are expected to range from a 3.5-liter V6 with 292 horsepower to the top-o'-the-heap 6.2-liter V8 with 525 hp. Rumored to be tucked in there as well is a 299-hp hybrid.

[Source: SpeedLux]