GM has gone to a great deal of trouble to assure there will be absolutely no range anxiety by accomplishing the difficult feat of engineering a series hybrid containing a complete electric propulsion system and then a complete ICE-generator system with a bunch of clever electronics that can kick in if the batteries run down. (Indeed, as the 16KWH battery pack only uses 8KWH of energy (from 80% to 30% SOC), it probably has to have some compromises in power-to-energy chemistry, favoring producible power over total stored energy.)
The following thought comes to mind: for those of us who are not paralyzed by the false fear of range anxiety, why not just ditch the whole complex ICE-generator-electronics system and, with 500 pounds thereby jettisoned and the engine bay thereby made available, just throw a bunch more batteries in there (with, presumably, a better energy chemistry)? I would guess that the
engine-generator-electronics-whole-shebang can't cost much less than $6000 wholesale, and assuming the wholesale battery cost of their lithiums is something like $400 KWH, they could probably put another 16KWH of batteries in there for around the same cost and a bit less weight. With better chemistry batteries that don't mind a bit higher and lower SOC (and of course, with an all-electric system there'd be no 10 year/150,000 engine emissions warranty issues to worry about), they could have at least 32KWH of battery, likely good for around 125 miles, with even better performance, for the same price.
There is no downside. GM should drop the other shoe and get to it.