It's going to have a rotary!
Mazda management have, it seems, changed their tack on spinning triangles. The new engine will be called "Skyactiv-R" and should debut at the Tokyo Motor Show.
With concerns about the rotary's ability to meet emissions standards, there has been no word from Mazda on whether or not it will have electric motors providing a McLarenesque "torque fill" and emissions-regulation assuagement or whether alternate fuels will be sought out. Mazda has hinted in the past at using a (gasoline) Wankel generator as a range extender on a purely-electric car. For a sports car, most of us would consider this to be a bad idea; not only is electric anathema to the noisy, dramatic, and somewhat fickle sportscar, it is doubly anathema to the rotary sportscar which exaggerates those characteristics still further.
In my completely unsolicited and inaccurate on-the-internet opinion, they will probably end up with a ~1800cc (swept, 3600cc equivalent) three-rotor arrangement with sequential twin turboes. To keep complexity and weight down, in keeping with the rotary mandate, I would posit that it will have a mild-hybrid setup à la first-generation Honda Insight. This setup has the electric motors between the engine and transmission for a minimal space and weight penalty. With an engine as short and as low as a Wankel, I do not think that Mazda should have any issues achieving a 50/50 weight distribution with this setup, thus negating a large advantage of placing the motors in line with the rear wheels. As the power from the electric motors will have to flow through the transmission and the differential, some efficiency will be lost, but I think the packaging advantages would be worth it in a car of this type.
All is speculation at this point so keep your eyes peeled. I, for one, think the render below looks fantastic and eagerly await its debut.