As per the tweet, Rockstar appear to be developing a new patch for Grand Theft Auto: The Trilogy - The Definitive Edition, according to recent activity on SteamDB - likely the new fixes and improvements from the mobile port.
This is actual real activity, not anything to do with Rockstar Games Launcher or changing encryption keys on Steam.
This is actual real activity, not anything to do with Rockstar Games Launcher or changing encryption keys on Steam.