The real question is how efficient is it?
It does not have to be any more efficient if they manage to reduct weight and increase reliability. Efficiency has a big part to play but even a less efficient engine would be desirable if they improve greatly on other aspects.
Remember that this is being targeted for vehicles that will run mostly on electric power. An ICE is a dead weight when not being used. If someone drives using 90% pure electric then the efficiency gains of carrying less weight could easily outweigh the losses of an ICE that was 5% less efficient but only operates for 10% of the time.