I mean that there are methods that do not rely on anything scarce that will come down in price to be well cheaper than coal. If, in the absence of scarcity, the thin film methods that do rely on the scarce elements would be even cheaper, it does not matter much. I would guess that China is using a lot of rare earths because they manufacture a lot of electronics. Indium in not technically a rare earth but it could prove to be a constrain on CIS and CIGS thin film solar cells: http://en.wikipedia.org/wiki/Solar_cell#Copper-Indium_Selenide

Chris