I'll follow and be brave like the first poster and speculate a bit.
Reduce performance requirements (speed and comfort to the level of a 90's Geo Metro, 3cyl. 1L) and the series-parallel type hybrid used in the Pirus could improve it's mpg greatly.
There's huge competition in hybrid market with a variety of different types of hybrids being developed not only to improve economy, but just as important, to allow the model to use THE 'hybrid' label. He who holds the right patents MAY dominate, yet an inherently inferior design if profitable, could be refined and survive, and possibly do well, allowing the manufacturer to stay in business. Different designs must be used to avoid patent infringement, and some are better than others. If you believe the first to market has the advantage, and is inherently the best possible design from which to succeed in the long run, in at least one segment, i.e. the Pirus, ATTACK IT, subvert it, down play it's importance, or whatever! Keep customers and investors on your side.
Vehicles are going though a radical change and ya gotta wonder how 4X's will be effected. I think it not so bad. I've watched the 'series'-hybrid diesels HUMV's develope. It's basically set up like a diesel/electric locomotive. The motor/generator only runs to recharge the batteries and provides no power directly to the drive train. Although with this type of hybrid, acceleration in the econo box might be unacceptable by today's standards, it appears to be the most efficient, just slow that's all. Battery technology will be a major factor in the improvement of these designs. It's mostly about weight.
Although I prefer something rugged and simple (read cheap and easy) to fix, hence an old 85' Toy, a series hybrid type diesel would be my choice. Imagine the useable low end torque of an electric motors on wheels, the control and power, and the ability to turn like a tank if you'd like. The electric motor(s) could drive the vehicle for 20 + min without the engine running, and the diesel/generator is built in ready to power all the toys, while doubling mpg or range! This HUMV is reported to get 16 mpg, over the previous 8. This improvement is huge for logistics.
I believe the series type of hybrid does best in large heavy vehicles because the batteries are heavy. The reason is that a higher GVWR truck can haul more weight efficiently than a smaller vehicle, even though it's mpg seems terrible. A tractor trailer (18 wheeler ) can get 8 to 12 mpg hauling 50,000lbs. That's allot of goodies.
There will be all kinds of flavors, but the diesel 'series' type of hybrid will have it's day. That's what I hope. It'll allow for some powerful and nimble rigs.
