Casper, Ethereum's proof-of-stake model, is coming soon™. Casper will slowly transition Ethereum from Proof-Of-Work to Proof-Of-Stake.

Ice Age

Ethereum developers foresaw the need to switch from the Proof-Of-Work model. Therefore, on September 7, 2015 they initiated the Ice Age. This code exponentially increases the difficulty of mining a block on the chain, thereby forcing a hard-fork and ensuring that the old fork dies out.

What does this mean for Ethereum?

Proof-Of-Stake will make Ethereum more like Steem, which is also Proof-Of-Stake. Instead of traditional POW mining, Hodlers of Ether will be required to vest their coins and validate the network to cash in on newly created coins. The only way to do this on Steem is to be a witness, but on Ether anyone with stake will be able to participate.

Instead of 10% of the reward pool going to miners (witnesses) like it does on Steem, Ether will be giving 100% of the rewards out to miners. Ethereum very well may use this as leverage to end their transaction fees, making it a much more friendly platform to use.

Like Steem, Proof-Of-Stake will fix many of the scaling issues Ethereum is having. Currently, they are operating at 100% capacity and are getting bogged down by transactions. By avoiding the "worthless" hashing work done by the Proof-Of-Work model Ethereum will use all that extra power to scale up and have much faster transactions.

Should Steem be worried?

As I've previously explained, blockchains do not compete with each other. A win for Ethereum is a win for every blockchain. There are many blockchains that are considered superior to Ethereum, but this won't stop it from expanding. Once SMTs are released, Steem might very well be superior to Ethereum in almost every way. However, that still won't stop people from using Ethereum. It is a tried and true blockchain at the top of the market cap.

Check out this article:
Porsche Launches Ethereum Based Blockchain Pilot to Smartify Cars

Why did Porshe use Ethereum when there are theoretically better options out there? It's pretty simple, a big company isn't going to take any risks with a more experimental blockchain. They want a sure thing.

Conclusion

Blockchain tech is evolving at an exponential rate. Just when you think a coin is going under they come out with an upgrade to stay afloat. The Blockchain is far from mainstream. We are all in this together. All blockchains are open source so we are all helping each other, not competing. The Lightning network will increase the value of Bitcoin. Casper will increase the value of Ethereum. STMs will increase the value of Steem. Every blockchain will have the opportunity to look at this new code and incorporate it into their own code-base. Every blockchain benefits.

Here's a few articles I read on this topic:

Ice Age:
https://www.coinstaker.com/ethereum-ice-age/
https://www.cryptocompare.com/coins/guides/what-is-the-ethereum-ice-age/

Casper Testnet:
https://www.trustnodes.com/2017/11/28/ethereums-proof-stake-casper-testnet-nears-launch

Summary:
https://coincentral.com/when-will-ethereum-mining-end/