The Prius put Toyota on the map as green car hero No. 1 when the hybrid arrived in 1997. But with the fifth-generation redesign just around the corner, the Prius' hybrid drivetrain faces a test for relevance.

Honda has plans for a massive transition to all-electric. But for now, it's focusing its energy of rolling out hybrids.

Brands have geared up for an EV future with some brands focusing only on electric models and dozens of plug-in nameplates soon hitting the market.