[SilasX]

Mining expenditures are limited by the benefits relative to the cost. Increasingly expensive mining is added until the expected revenues of bitcoins sold don't make up for them. At the moment right now, more mining could come online, but isn't taken online because it wouldn't pay for itself.

If energy becomes more expensive -- say, by pricing in the externalities of some energy sources -- that decreases the equilibrium expenditure, because marginal mining can't pay for itself anymore.

The concept of "pricing out miners" doesn't even make sense to begin with. Miners are competing with other miners (including malicious ones). Any resource constraint affects all of them; it can't make all of them give up. To the extent that other coins become popular, that (again) just prices out marginal miners.