Ethereum is going Proof-of-Stake within, oh, maybe 6 months in the Serenity release using the Casper PoS algo...
So the Ethereum Global Supercomputer (EVN) that serves blockchain features via Turing-complete custom functions...
Will have a fixed amount of "gas" to pay for cycles (ETH)... which will circulate endlessly throughout the ecosystem.
https://blog.ethereum.org/2015/12/28/understanding-serenity-part-2-casper/
It's as if there was a fixed amount of energy on earth in the form of "energy tokens"...
And the exponential increase in human energy usage MUST translate into exponential increase in the value of "energy tokens".
Right now ETH is doing > 30,000 tx/day with no large commercials apps yet released...
Exponential growth in both tx/day... and the price of Ether is a good bet due to the PoS rollout.
https://stats.etherchain.org/dashboard/db/transactions?theme=light
Bitcoin is down 50% since late-2013 and developing at a truly glacial pace...
So if you wanna speculate on a crypto-ecosystem that could blow by Bitcoin by orders of magnitude in 12-24 months... don't expect "cheap".