If the horses are real and not ponies and the connecting rods are less elastic than the current ones... (and I've posted here about the current BMW M3's unfortunate tendency to grenade it's motor) Well, sure, somewhere around 5 seconds isn't unrealistic. A stock S70 T5 manual will do it in 6.1 and that's with "only" 236hp. Sub 5-seconds? ... let's see!

From Edmunds:

Volvo has officially announced its intention of entering the high-performance luxury sport sedan market with the new S60R. Although Volvo is hardly the name that pops in most enthusiasts heads when they think of seriously fast sedans, the S60R stands a good chance of changing that perception. Under the hood will rest a 2.5-liter turbocharged five-cylinder producing 300 hp and 295 lb-ft of torque at a low 2,100 rpm. A choice of either a six-speed manual or five-speed automatic will send the power to the pavement, while an electronically controlled Haldex all-wheel-drive system should ensure tenacious grip in the corners. The S60R will introduce a unique adaptive ride control system Volvo refers to as "Four C Technology." The Continuously Controlled Chassis Concept uses multiple sensors to detect road variations and adjust shock damping accordingly. The system will also give drivers the option of three ride control settings: Comfort, Sport and Advanced Sport. Further enhancing the S60R's performance cache will be four-piston Brembo brakes, Servotronic steering and a standard Dynamic Stability Control System (DSTC). Production is slated to begin early next year in Volvo's factory in Ghent, Belgium.