They were the last car makers to hold out but now even supercar manufacturers are investing large amounts of time and money into building high mileage cars. They're worried about possible falls in sales if they don't build more environmentally friendly cars than at present. Also, they need to meet tough new CO2 regulations which will be in force in Europe by 2014 and the U.S. in 2016. Supercars are easily the worst offenders for bad fuel efficiency. The Lamborghini Murcielago for example uses gas about six times quicker than a Smart Car!
Lamborghini have said they'll reduce their vehicles carbon dioxide emissions by 35% by 2012. But they don't have a clear vision as yet on how they're going to do this. Lamborghini just say they're looking into several fuel saving options such as hybrids and biofuels. However they will definitely be reducing vehicle weight through the use of lighter materials and will be developing existing engines into more fuel-efficient units. Lamborghini have budgeted US$50 million to research and develop high mileage cars over the next 5 years.
Ferrari are probably closer to producing fuel efficient vehicles. They've already tested a hybrid engine in their 599 coupe and plan to be selling a hybrid supercar by 2015. Ferrari have set aside half of their total research budget to building greener cars.
Porsche will have hybrid cars for sale from 2011, although only hybrid versions of the Cayenne SUV and Panamera sedan, which are only sports cars at best, not supercars. Indeed at this point in time they do not intend to make a hybrid 911, which is their best car.
Ferrari and Porsche have both stated they will never make all-electric versions of their cars because of the loss of engine and exhaust noise. If electric sportscars become massively popular I think they will go back on this, otherwise they'd be losing a lot of potential customers, at a time when the internal combustion market could be dwindling.
A few years back I never thought we'd soon be discussing high mileage sports cars! With the current green revolution it'll be interesting to see if sports cars and supercars remain as popular in the future as they currently are. Car makers are certainly working hard to keep them changing with the times.