[alexkcd]

So long as mining remains profitable, as it has to be in order for anyone to spend resources on mining, the energy race will continue. As mining profits decrease over time, so too will the pool of miners who are able to mine profitably.

The network will, as a result, centralize over time to a select few that have access to cheap and plentiful energy. These "big energy" :) companies will control most of the hashing power.

You can already trace this with bitcoin by looking at who the early miners were versus who the miners are now.