Conversions take time and money. Also, natural gas prices are not going to stay low forever. Maybe for a while, but not indefinitely. Also, the EM's (e.g. China, India, etc.) are still going to build a lot of coal fired plants. Its probably more foreign markets that will drive costs more than the US market.
Coal will go down cyclically, and then become a good valuation play. In the US mines may have to be shut down before we bottom.
I would like to see BTU do stock buy-outs of some of the other US players. I don't want any more debt on their balance sheet, but if they could acquire other companies when the price is low, it would probably work well in the L-T.
On a BTU versus cost basis, coal is cheaper than $2.35 Mcf gas. The big extra cost for coal is the carbon cost.