Mining bitcoin is essentially printing money, so miners with profitable setups have an incentive to expand these setups. As mining capacity grows, a parameter called "difficulty" - which represents how much power you need to waste to mine a block - is adjusted so that the mining rate remains constant. Since mining is necessary to maintain network security, difficulty will grow to compensate for expanding mining capacity, but not high enough to kill it off.

If you look at the history of the adjustments to difficulty, you'll find a pretty much clean exponential.

(In other words, Bitcoin is as close as we've ever come to expressing greed in units of kilowatt hours.)