The new mode would delete your save file if you died.
Developers CD Projekt RED have revealed they are looking at an "Insane" mode for The Witcher 3: Wild Hunt, which would severely punish players in the event of their death in-game.
Talk of the Insane mode was heard in the livestream the devs held on Monday, however they didn't linger on it too much as it's still in development.
One idea for the Insane mode that the developers spoke of was that dying just once would delete the save file.
Game Informer reported that CD Projekt RED want Insane mode to be punishing, but fun. No other details about the mode have been revealed, but remember that this is just an idea at the moment and may not even make it into the game.
The Witcher 2: Assassin of Kings had couple of higher diffulty modes - Isane and Dark - which increased enemy difficulty and had penalties for dying.