Do everything? Or complete the main story campaign?
I've beaten the main story campaign in the Witcher games numerous times, but I've never 100% completed everything a Witcher game has to offer.
I suspect Cyberpunk 2077 will be even more of a challenge in terms of me complete things; heck, it already seems like they've blown Witcher 3 out of the water in terms of stuff to do and replayablility, and we haven't even seen what the future paid/unpaid DLC/expansions.
Game's like these aren't meant to be completed, you just keep playing them; like an elder scrolls game or a grand theft auto game.