Audi’s A4, in all its variants, is the company’s best-selling car worldwide. The current B8 version was debuted to the public at the 2007 Frankfurt Auto Show, with sales beginning in 2008. While the car gets a light refresh for the 2013 model year, it will soon be due for replacement.

The new model, designated the B9, is expected to arrive in sedan form in 2014, followed by a new A4 wagon in 2015. As Car Magazine reports, there are some significant changes allegedly in store for the next generation of Audi’s compact sedan and wagon.

First, the car will be built around the Volkswagen Group’s MLB Evo platform, which promises lighter weight, improved stiffness and greater versatility. Car quotes sources close to the project as saying that the B9 Audi A4 will weigh some 220 pounds less than the current version, aiding with both performance and fuel economy.

The biggest news may come in the form of changes to Audi’s legendary quattro all-wheel-drive-system, with an electric-based system called e-quattro reportedly under development. Deleting the bulk of mechanical components needed in today’s quattro drivetrain would further reduce weight, and an electronic AWD system could be tuned for more precise handling.

The e-quattro system would allegedly use a pair of electric motors with a combined output of 136 horsepower to drive the rear wheels, while the internal-combustion engine would supply power to the front wheels only.

The e-quattro system would require a plug-in-hybrid drivetrain, which is also rumored to be under development in a front-wheel-drive configuration. Front drive A4 hybrids would likely incorporate an electric motor within the transmission for ease of packaging.

Expect the next-generation Audi A4 to benefit from improved gasoline and diesel engines, too, with gains in both output and efficiency likely.