Ethereum developers are already implementing code for Constantinople, the network's next system-wide upgrade.

The second part of a series of upgrades to make the ethereum network more efficient and less costly in terms of fees, Constantinople will be activated sometime before October's Devcon4 ethereum conference, according to stakeholders during a core developer meeting Friday.
That said, an exact block number at which the code would go live hasn't yet been confirmed for the backward-incompatible change.
A loose roadmap for the upgrade has also been suggested. Under that roadmap, the implementation stage continues until August 13, after which there will be two months of testing, including the launch of a Constantinople-specific test network.
The upgrade will include various optimizations aimed at making the platform more efficient – and less costly in terms of fees. Constantinople is the second part of a two-part series of upgrades, following in the footsteps of Byzantium, which was activated last October.

According to the meeting, a total of four ethereum improvement upgrades (EIPs) are currently being implemented by developers. Péter Szilágyi, lead developer of Geth, the most popular ethereum client, said they have already implemented most of the changes.