to maximize profits of BTC mining, cheapest possible electricity is required. therefore, the problem solves itself. sure, i may not want to drop 10,000 USD (1 btc.
) on a solar system for my home, but hell, if i run miners as well, they're obviously, unquestionably reach a return on investment, eventually. because if you're not paying for electricity, but just the 1-time cost of panels and miners, they can run forever. even BFL miners could turn a profit under that circumstance.
therefore, eventually the big miners will switch to renewables like solar and wind. to not do so is to waste money.