This is different from the impression I previously had, which was more along these lines:
http://www.economist.com/blogs/graphicdetail/2012/12/daily-c...
Where do you get your impression from?
Most of the reduction in that Economist graph is after Obama takes office, before that the changes are not all that dramatic to really support a comparison to Moore's law (which has itself shown pretty flawed as a way of predicting the computing future).
So I just don't see any substantive, fundamental reason (i.e.: clear prospect) to suppose that solar generation will get so much cheaper that it will reach striking distance of natural gas, of which we have quite a supply. But I'm not saying it's impossible to have another opinion.