It should be noted than 25kW is 33HP. Though it's possible to make a useful car with that little power, 33HP is generally considered an appropriate power level for a beginner's motorcycle, not a car. Even if it's much lighter than a piston engine and has such a wide powerband that it doesn't need a gearbox, it's likely they'd need a lot more power for consumer acceptance even in small cars.

Edit: I googled this and found that the intent is to use this engine to run generators to charge batteries in hybrid cars, not for direct propulsion. In that case, the cars probably won't be much, if any lighter than standard cars since all the weight savings will be replaced with batteries. Power output could, of course be lower than a standard car engine and still provide good performance since the electric motors could have peak outputs far exceeding the sustained output of the generator.