To use your comparison, CEOs selling solar panels are responding to scepticism about the stability of that supply and its elasticity to fluctuating power demand with vague promises of developing more advanced cells that can operate with less light and throttle the generated power during ebbs in demand. They buy land to install more solar panels, then lobby for the deactivation of other, flexible power sources that could supplement their supply until they can finally start charging more in times of high demand.

To be honest, it seems to me that are not the CEOs of solar panel companies that belive that solar panel (and other renewable sources) are a drop in replacement for more traditional sources. This idea comes from a certain area of the political spectrum and groups that do not understand even the basic math behind the substitution of a gas turbine with a field of solar panels.

Then it is true, CEOs are probably overselling, like everyone that has to sell something. And obviously they need to say that the technology will improve otherwise in the current economy they will be ignored and investment would go to other things.