I am waiting for the diesel hybrids, that should bring the best from the both worlds.
Guess they would be very heavy with the extra weight of the diesel engine at the front
and the batteries at the rear....
AFAIK the modern diesel engines are not significantly heavier than petrol engines of same cylinder volume.
The turbocharger does add some weight, and that's about it.
Hyundai seems to be using lithium-polymer batteries wityh that hybrid. That kind of batteries have quite high energy density, for a light hybrid use such battery could be put to the space reserved for the spare wheel.