Audi R8 E-Tron in red on auto show floor

Throughout its brief history – from concept car at the 2009 Frankfurt Motor Show, to production-bound prototype – the Audi R8 E-Tron has promised supercar levels of entertainment in a sexy German wrapper. A prospective range of 150 miles with acceleration on the order of 0-60 in under five seconds suggested a more luxurious rival for the Tesla Roadster, and a challenger for the upcoming Mercedes-Benz SLS AMG Electric Drive at the E-Tron's expected launch in early 2013.

Now it seems like Audi may have slammed on the regenerative brakes, as it were.

Car and Driver reports that the R8 E-Tron plan is on hold, pending a project review ordered by new research and development head, Wolfgang Dürheimer. Concerns about the project include a lack of sufficiently advanced and reasonably inexpensive batteries with which to power the car, as well as a buyer pool sufficiently rich and reasonably motivated to drop big sums on the R8 EV.

The Car and Driver report indicates that the expected launch in the first part of next year is now off the table, and that the entire project faces existential jeopardy.

UPDATE: We were able to speak with a member of Audi's team regarding the fate of the R8 E-Tron, who basically corroborated the earlier Car and Driver report, with a few clarifications. Audi claims that the "initial" run of R8 E-Trons was always meant to be very limited (ten cars), and that those cars were essentially meant to serve as evaluation models for the project as a whole. The discrepancy seems to be in what eventually happens to this first run; first plans indicated that they would end up in public hands, while now Audi states that they are "primarily intended for internal purposes."

On a positive note: While the future of the R8 E-Tron looks pretty cloudy (at least in the pure-EV form), we're told that the A3 E-Tron is still on track for arrival in 2014.