The announcement may take place at The International 2019.
Valve registered the Dota Underlords trademark on May 9th. According to the description – this is some kind of video game software.
Gamers have already put forward the first assumptions: they believe that the upcoming Valve title could be a VR game, Dota spin-off, an extension for Artifact, or a mobile application.
Perhaps the announcement will take place at The International Championship 2019, which will be held in late August.