Fully electric RV, diesel generator, RV of the future?

Diesel electric with battery backup....old tech with modern components. The Navy has done that for many decades with both submarines and now surface ships. No doubt is can make it's way into commercial/recreational vehicles sometime in the future. Energy storage density needs to sky rocket and I suspect it will still take a rather large engine.

My coach uses ~200 hp to move it at 63 mph on level ground and ~500 HP on grades. Figure driving 6 to 8 hours a day....that is one huge battery and very large motors.