A prospective BMW i4 could blend characteristics from the expensive i8 plug-in hybrid and the small all-electric i3.

BMW’s i line of electric vehicles will extend beyond the confirmed i3 all-electric car and the i8 plug-in supercar. We’ve known that at least since May 2011, when PluginCars.com contributor Tom Moloughney reported on the various sizes of electric cars that BMW was considering.

The idea that BMW could produce a plug-in car with slightly more room than the i3—and one that possibly uses a gas engine to extend range—makes good sense. In the past year, small EVs have been outsold by plug-in hybrids. The dramatic BMW i8 plug-in hybrid has received a lot of attention, but with a price tag likely to exceed $100,000, it’s an ultra-niche vehicle. Both of those vehicles are slated for production late next year.

So, if BMW is serious about electric cars, we can believe rumors that the company will unveil an i4—a car that could split the difference between the i3 and i8—at the upcoming 2012 Los Angeles auto show.

Few details are known at this time. Tom’s report suggested that a larger-than-LEAF car—what he, at the time, called an “Urban Commuter Vehicle”—would not go into production until 2017, although media sources speculate that an i4 could go on sale as early as 2015. It’s common in the auto industry for a vehicle to travel from concept to production in about four or five years.

The first mentions of an i4 (and an i5) occurred on the web in August 2011. These reports should be taken with a grain of salt, because BMW has not officially confirmed anything. But what can we glean from those reports? Here are the highlights:

• The i4’s architecture will be based on the i3, which is expected to deliver 0-62 mph performance in less than 8 seconds from a 170-horsepower electric motor.
• The i4 would offer a plug-in electric or range-extended electric drivetrain, perhaps with 600cc twin-cylinder gasoline engine.
• BMW is committed to using carbon fiber construction.
• In term of appearance, the i4 will look sportier than the geeky i3. It could have a low sloping roofline and wider stance. And it could be a four-seat coupe, rather than a four-door i3. At least in the concept version, the i4 could have rear-hinged doors.
• It's likely to be more expensive than the i3, which is expected to be priced around $50,000.