Mazda started developing the next Renesis engine (16X) back in 2007 but it hasn't made it into prodution for several reasons, not the least of which was (surprise surprise) the inability of the engine meet tougher fuel economy standards. There's no serious replacement rotary engine (or sportscar host for it) in sight, but Mazda puts out a new rumor and a couple of design sketches every year or two to keep rotary enthusiasts' hopes up. It's kind of mean.
RX-8 gets similar mpg as a Z06, which makes over twice the hp/tq. My dad's former track car was a 3rd gen RX-7 with a single T88 running something like 26-28 psi and making well over 500 whp on race gas. It got 4 mpg on track, same fuel mileage as a Learjet.