Ethereum Core developers have decided to implement EIP 1234 (Ethereum improvement proposal) in the upcoming Constantinople upgrade. EIP 1234 entails a reduction of the block reward from 3 ETH to 2 ETH, slowing down Ethereum’s inflation rate. EIP 1234 was decided upon as a compromise between another proposal that recommended the block reward to be reduced to 1 ETH and a proposal that recommended that the block reward stays the same. The implementation of EIP 1234 is not yet set in stone, as the proposal could undergo additional changes.

The proposal also includes the postponement of Ethereum’s “difficulty bomb” for 12 months. The difficulty bomb will make mining Ethereum much more difficult and is baked into Ethereum in order to make the switch to proof-of-stake (Casper) easier. If Ethereum is still profitable to mine when Ethereum is ready to upgrade to Casper, miners might stick with the old chain, resulting in a hard fork.

Unsurprisingly, the proposal is not popular among Ethereum miners, as the block reward reduction lowers profitability for miners and can make certain computer hardware too inefficient to mine Ethereum at a profit. This could result in the Ethereum network declining in hashpower and therefore becoming less secure.

By lowering inflation, however, EIP 1234 will likely have a beneficial effect on the fiat value of ETH. A poll of ETH holders unsurprisingly favored the more extreme EIP 858 (reward reduction to 1 ETH) as that could push prices even further.

EDIT: Please note that this poll only contains a small sample size (170), so it can't be taken as an accurate representation of the Ethereum community or ETH token holders at large.

The Constantinople upgrade is expected to be released in late October or early November. It will also include four other EIPs which are mostly uncontroversial: EIP 145, EIP 1014, EIP 1052, and EIP 1283.