i cannot imagine a Wankel coming back since there is no way to prevent the inherent flaw of the design: a combustion chamber with such a shape that high heat losses are unavoidable - leading to a high specific fuel consumption and emissions. the emissions can be tamed by aftertreatment, the heat losses and thus high fuel consumption and CO2 emissions can not. the original Wankels did have other problems: machining and the non-availability of suitable materials to make them last long were the main problem. those problems have been solved but the low efficiency has not.
thus, as a main propulsion unit it will not come back. used as a range extender is another matter. range extenders usually produce little power and are only meant to get you to the nearest socket so you can "fill up" your batteries. that means that the range extender will only contribute a small part to the emissions in terms of grams per km travelled and the small size of a Wankel unit might be favourable finding a suitable spot for it.
Agree. For small outputs the Wankel has the advantage of being smooth, simple and vibration free, especially comparing a single rotor Wankel to a single cylinder recip.
