According to a Rockstar Support article discovered by GTAForums member alloc8or, Grand Theft Auto Trilogy: The Definitive edition will have increased draw distances, GTAV styled controls and more.
All three games (GTA III, Vice City and San Andreas) will feature brilliant new lighting and environmental upgrades, high resolution textures, increased draw distances, Grand Theft Auto V styled controls and targeting.
Rockstar Support has also stated that if you buy GTA Trilogy on the Rockstar Games Store or via the Rockstar Games Launcher before 5 January 2022, you’ll qualify for a $10 discount on your next purchase of $15 or more on those platforms. The discount expires 16 January.
While the Rockstar Support article isn’t currently live to the public, we do know the URL that it will appear at: https://support.rockstargames.com/articles/4407663218067