BMW fans rejoice. The gas-powered M3 will likely retain six-cylinder power and avoid the latest engine downsizing trend that affected its four-cylinder-powered arch rival, the Mercedes-AMG C63.

The 3-series is the quintessential Bimmer, the automaker's compact bread and butter, and the M3 carries near-biblical levels of reverence among enthusiasts. The i3 will be BMW's biggest attempt to ...