Solar cell record efficiency is 46%, that only gives room for 1.12 doublings theoretically, and thermodynamics is nasty in the real world so we probably cannot even get past 1 doubling from here.
Modern rooftop solar modules haven't even doubled efficiency from 40 years ago, but they have improved cost per kilowatt hour by more than 100x.
My personal philosophy about technological progress is based heavily on the idea that material science is the principle barrier to what we can accomplish. That's why humanity's progress is recounted in "ages" named by material.
So, I think solar panels can get maybe 2-10x more economical, whereas other options like new hydrocarbon sources, fission, and fusion can probably all get at least 10x more economical than the maximum possible with solar, purely due to the physical limitations of the technology.