Unless people in the future become religious nuts even worse than today's, I don't see why they'd waste so much space and resources on power-generating burial mounds. The pyramids may be impressive for a primitive civilization to build, but they were functionally completely useless and just a collosal waste of manpower, materials, and space.
This is quite unlike solar-power-collecting terra cotta roof tiles: roofs serve a real purpose, on buildings that people live and work in.