It is too early to tell, but it can be a simple localization-related fix for the game. You can see that the files that were altered in this update include the main binary files for The Witcher 3 and speech files in the various languages. Steam Database has listed the files that were changed in this update, and it mostly seems to be for the localization.
It doesn’t seem to come with any official patch notes from the developers.
The Witcher 3 has received a new update on Steam out of nowhere.
