GM announced that it will introduce two new electric plug-in hybrid vehicles in the next few years based on the early success of the Volt. One of those is likely to be a plug-in version of a Cadillac. Speaking at an auto show, GM CEO Daniel Akerson said the company was increasing this year’s sales forecast for the Volt from 10,000 cars to 25,000. The Volt travels 25 to 50 miles on a fully charged battery before switching over to a gas engine. Akerson said that technology can get a lot more efficient but that Volt is a sign of what’s possible.