BMW is continuing the development of the new 3-series sedan, internally called the F30. Captured here by our spy photographers near the Nurburgring race track in Germany, the four-door prototype is still under heavy camouflage, thus revealing little about its exterior styling.

However, buyers should expect an evolution of the current design sprinkled with styling cues from all the latest BMWs, including a protruding kidney grill similar to that of the new 5-Series and 7-Series saloons.

Our man with the long lens managed to snag a few shots of the prototype’s interior giving us a glimpse of the new dashboard design with the 1-Series-esque air-vents.

Munich’s best-selling model will continue to be offered with a large variety of gasoline and diesel engines. However, the big news here is that BMW is working on a new generation of 4-cylinder gasoline engines with single- and twin-turbocharging, direct fuel injection, and stop/start systems.

It is believed that the four-pot turbos will be offered with a displacement of 1.6- and 2.0-liters producing up to 230HP in standard guise. More powerful versions could follow.

Of course, the Bavarian automaker will continue to offer its trademark inline-six powerplants, including new variants of the 3.0-liter twin-scroll turbo unit that makes 306-horsepower and 400Nm (295 lb-ft) in the current 335i.

The diesel lineup will comprise of four- and six-cylinder turbocharged units, all equipped with start-stop technology.

There’s also a strong possibility that BMW may introduce a mild-hybrid variant, but this has yet to be confirmed.

BMW’s M division is preparing a successor to the M3, however, it is not clear whether it will keep the current model’s naturally aspirated V8 unit or, as rumors suggest, be offered with a newly developed straight six twin-turbocharged unit with direct injection.

Once again, the new 3-Series will be offered in a number of body styles, including Touring, Convertible and Coupe models with a crossover-ish GT variant akin to the 5-Series Gran Turismo said to be under consideration.

Expect to see the new 3-Series in sedan form at BMW dealerships sometime in 2012 with the rest of the range to follow after.