The expected hard fork for Ethereum is already running in test mode. The Byzantium update is part of the Metropolis stage of the Ethereum project. The tests will run for about three weeks to see if any unforeseen problems arise. The official change to the network should come between October 9 and October 18, depending on test results.
The developer team may also come up with a formal date for the hard fork in the next few days.
The update aims to decrease attacks on the network, and allow for the use of advanced cryptography on the Ethereum blockchain.
The Ethereum network will be undergoing a hard fork at block number 2463000.
After the fork, the Ethereum blockchain will work with new rules. And clients will need to upgrade to the new rules, or lose their tokens. To synchronize to the new rules, the users will need the appropriate versions of the Ethereum client:
You can observe the experimental blockchain here. Byzantium is the first stage of the Metropolis update for Ethereum, so one more update is expected. The final stage for Ethereum will be Serenity, when the currency does away with mining and turns into a proof-of-stake cryptocoin.
The Ethereum Mining Difficulty Bomb
The Ethereum project eventually wants to switch to proof-of-stake consensus. For this, mining needs to become unrealistically difficult. The intention was to increase difficulty back in 2016, predicting the end of mining. But the code was changed just in time, as the updates to the system lagged and still have not materialized.
But not even the Metropolis stage would bring the Ethereum Ice Age that stops mining. A recent GitHub commit shows that the difficulty bomb has been delayed by approximately one year and four months.
The solution, for now, is to use a "fake block number" to ensure the old level of difficulty. On the surface for Ethereum mining, things should go on as usual, and Ethereum is not going to mutate overnight into a differently organized blockchain. If you prefer proof-of-stake coins, try out Dash, where there are a series of Master Nodes that approve consensus and pay for this by owning and holding 1,000 DASH.
So while the rules for the network may change, for a general Ethereum user or investor running an updated wallet, the changes would not be felt, and only the market price would matter to make decisions on Ethereum.