Toyota could be planning a more sure-footed version of its popular Prius.

We've already heard rumors that Toyota is planning to alter the iconic wedge shape of its next-generation Prius, and now comes word that the Japanese automaker is also planning a major shakeup for the hybrid's powertrain.

Since its inception the Prius hybrid has been a front-wheel drive vehicle, but Auto Express reports that could change when the new version of the hybrid debuts in 2015. Toyota is reportedly planning an all-wheel drive setup for its popular gas-electric.

A Toyota insider revealed to the British news outlet that the next-gen Prius will adopt a four-wheel drive system similar to the one employed by Peugeot.

"The rear wheels will be driven by a motor in an e-4WD system," the insider said. "Targeting snowy areas, they will operate at up to 37mph."

The plug-in version of the next Prius will also adopt the all-wheel drive layout.

Although all-wheel drive systems have a tendency to ding fuel economy, the e-4WD system will avoid that. In fact, Toyota is said to be targeting 90mpg for the 2015 Prius. That giant leap will be made possible by improvements to the car's current gas-electric powertrain.

"The current 1.8-liter engine will be modified, while the inverter and motor will be downsized, but will deliver more power," the source revealed.

Toyota will stick with a nickel-metal hydride for the standard Prius - likely for cost reasons - but the plug-in variant will use a lithium-ion unit.

On the styling front, the insider confirmed that the Prius will lose its signature wedge shape.

"The bonnet height will drop by at least 90mm and the car will lose its wedge shape. The A-pillar will move backwards and the roofline will be pushed forward by around 500mm."

No word on when Toyota might unveil its next Prius, but we don't expect to see the car until at least 2014.