With the slow but eventual death of Mazda's RX-8 in 2012, the Wankel rotary engine fell out of use in road-going production cars. Despite its incredibly simple design -- with just three moving parts -- it had developed a reputation for being unreliable, oil-burning and fuel-hungry. But a new report out of Japan suggests the rotary, loved by enthusiasts for its distinctive brap-brap sound and driveability, might make a return -- in a new Mazda RX-9 at the beginning of the next decade.