Integrated solar charging and incorporating batteries and panels that are already a necessary part of the vehicle has been and will continue to be the way to keep boosting range.
I think the biggest thing that people assume incorrectly is that there will be big strides in battery efficiency building on liquid state batteries. Most of the gains have been to make them cheaper or through incorporation in the design, reducing overall vehicle weight. The actual decreases in battery weight or increases in energy density have been pretty small, and it's really down to a surface area to volume optimization, which can't really be improved. Change in materials have helped some, but by the time you apply that to overall weight and energy density, you are talking about minimal gains to range.
After that it probably takes a step change, where solid state batteries are proven out and can be produced at a reasonable cost.
Right now most EV's can go farther than most people's bladders, so I don't think a huge boost in range is nearly as important as increasing charging rate and a huge boost in stations.
If they can boost the infrastructure and get the gains in range through the best integration of the batteries and panels, like you suggest, there will be massive adoption in light vehicles. It's going to work for nearly everybody. Spending a bunch of time and money to get convert the guy that thinks he's going to pull a full horse trailer on a 110 degree day through the Nevada desert is a waste.
