UPDATED | January 18, 2019
The Constantinople hard fork has been rescheduled for block number 7,280,000, and will not include EIP 1283.
The estimated date of arrival is now February 27, though due to the difficulty bomb (which has already started to take effect), it is difficult to calculate the exact time at which the Constantinople block will arrive. The difficulty bomb, if you're unaware, causes block times to slowly increase over time, reducing issuance.
ORIGINAL | January 15, 2019
Turns out Constantinople will not be arriving tomorrow as expected.
On Tuesday, auditing firm ChainSecurity discovered a bug in one of the five EIPs slated for the upcoming hard fork. Ethereum Improvement Proposal (EIP) 1283, the proposal to adjust net gas metering for the SSTORE opcode, was found to have a security vulnerability that would allow reentrancy attacks.
As ChainSecurity explains in a Medium post about the bug, an attacker could exploit the vulnerability to repeatedly steal other people's Ether out of a PaymentSharer contract. Though the auditing group has so far been unable to discover any vulnerable smart contracts, its scan for potential targets continues.
In the meantime, core developer Afri Schoedon announced on Twitter that Constantinople has been delayed. When it arrives, he stated, EIP 1283 will not be included. It has also been suggested that it could be included given some minor changes, but it does not appear that consensus has been reached either way.
In other confusions, Evan Van Ness, creator of Week in Ethereum, stated that the new fork date will not be chosen until Friday, during the next core dev call. However, Schoedon tweeted that the fork will take place on Monday.
In any case, the Constantinople hard fork will not happen tomorrow. Let the memes begin.