Toyota Prius Spy Shot

If you were holding off buying a new car in anticipation of the fourth-generation Toyota Prius arriving in 2015, your wait might be a little longer. Company insiders are claiming that production of the bestselling hybrid is being pushed back from spring to possibly as late as December 2015. Toyota is reportedly still making alterations to make sure everything is just right before it unleashes the all-important, efficient hatch on a waiting public.

According to unnamed sources speaking to Automotive News Europe, the main reasons for the delay aren't completely known. It's believed the engineers are still working on making the hybrid powertrain more efficient and improving the new Toyota Global Architecture modular platform. The insiders claim that the final production prototype of the Prius is still under development, and it might be November before it's finalized. From there, it usually takes around 12 months to tool up and for the first car to roll off the assembly line. It would be another year after that before the plug-in variant starts assembly. The national manager of Toyota Product Communications, Michael Kroll, told AutoblogGreen, "As you might expect, we can't comment on future product plans."

Despite the delay, some potential details have already emerged about the new hybrid. A company spokesperson recently told Autoblog via email that Toyota is engineering the next-gen Prius to have smaller, more power-dense electric motors and greater thermal efficiency. The new modular platform is also rumored reduce weight, and the changes could lead to a targeted 10 percent improvement in fuel economy.

One big upgrade won't be coming to the new generation immediately, though. Toyota product planning boss Satoshi Ogiso tells Automotive News Europe that the automaker's new silicon carbide semiconductors, which will reportedly increase fuel economy by 10 percent on their own, won't make it to the Prius until at least 2020.

Autoblog reached out to Toyota for official confirmation of the Prius' delay but was told that "the company cannot comment on any future product details."