Ruf Electric 911
The main obstacle has been, and still is battery technology. Though with Saft, Panasonic, Johnson Controls, Continental, and many others are working on it, how much progress will be made in the next year or two?
And when those batteries are suitable for automotive use and the technology accessible to niche players, think of how many more companies will be producing electric cars. Tesla is but one of many.
Ruf, the respected German firm that specializes in Porsches, has been working on an electric 911 of its own. So far it's not yet competitive with a gasoline powered 911, but it might just indicate where we are headed and what might be possible not long from now: