Rockstar Games has just pushed a server-side update for the Launcher, revealing that GTA Trilogy: Definitive Edition is almost ready for preorder.
This news was revealed by alloc8or and TezFunz2 on GTA Forums. Tez has discovered that the update added the Steam IDs for each Unreal title.

alloc8or discovered the Prepurchase/Preorder screens for the Rockstar Launcher. While no price or release date was leaked, more news about that should be just around the corner.
The GTA Trilogy backgrounds for the launcher have also been discovered.