The Ubuntu 17.10 release schedule has been firmed up and is now public. The Ubuntu 17.10 release date is slated for 19 October. For that to happen, the alpha release for opt-in flavors is 29 June, the feature freeze is 24 August, the beta is set for 31 August, and the kernel freeze is 5 October. That's assuming no delays, but Ubuntu's release cadence doesn't tend to be like Fedora's.
The Ubuntu 17.10 release schedule can be found via the Ubuntu Wiki. This cycle should be interesting as it's the one before the next LTS (Long Term Support) release so it tends to be more ambitious to get the changes in this round for vetting before the LTS release. Obviously it's more exciting as well due to the switch from Unity 7 to GNOME Shell and the likelihood of using Wayland by default. We also may see the new Ubuntu Server installer this cycle, integration of GCC 7, Mesa 17.2 or possibly Mesa 17.3 this round, and around the Linux 4.13~4.14 kernel. An exciting six months ahead!