The newest Prius has a solar roof option, which in good conditions seems like it can reclaim a few miles of driving range per day. We're a far cry from "never plug in", I think.
It seems like an incredibly useful tool for avoiding being stranded but I expect we're many years away from a vehicle that run optimally on solar power even in a desert.
It doesn't help with being stranded on any normal car. Better off walking.
It's more of a "unlimited AC when parked" than a "unlimited range" type of thing