Ubuntu 19.04 Is The "Disco Dingo"
According to this Launchpad entry, Ubuntu 19.04 is codenamed the Disco Dingo. The Disco Dingo is the six-month non-LTS successor to the Ubuntu 18.10 Cosmic Cuttlefish. The last time there was a DD codename with marking the entire Ubuntu alphabet was the Ubuntu 6.04/6.06 LTS Dapper Drake release.
archive.ubuntu.com has also been updated to reflect the new Ubuntu "Disco" archive.
Ubuntu 19.04 will be due out next April and be derived from the Debian Buster/Testing package-set and likely be using the GNOME 3.32 desktop components and a variety of other packages. More details as the Ubuntu 19.04 Disco Dingo development gets underway.