Ethereum's core developers have agreed to delay the Constantinople hard-fork until January 2019, in a meeting on Friday, October 19.
Constantinople entered testing on the Ropsten testnet on October 13 and had been planned to be activated on the mainnet in the October-November timeframe of this year.
During an hour-long meeting yesterday, the core developers reached an agreement that Constantinople would not be activated until January 2019 "at the earliest".
After Constantinoples Ropsten testnet debut it ran into a series of issues, initially with the fork to activate on block 4,230,000 and having stalled for two hours at 4,299,000. This stemmed from a "consensus issue," that triggered a three-way fork between Geth and Parity.
Schoeden outlined in notes released prior to that meeting “[r]ecently added hashpower caused reduced blocktimes and caused this hardfork to happen much earlier than expected on a Saturday,” which he stated “by all means the worst time for a hardfork.”
The fork happened six days after Geth's latest client release and one day after Parity's giving insufficient time for users to perform the upgrade. Developers also discovered a consensus bug within Parity. Additionally, the community does not have a testnet monitor.
Constantinople is a system-wide Ethereum upgrade that is intended to increase efficiency reduce the block reward for miners, and make the chain more ASIC resistant.