In case you missed the news, the update will be released on September 21. Despite the compatibility, the developers suggested that players should start fresh as, in their opinion, all the changes and new mechanics provide a different experience.
In case you decide to play with your existing saves, a skill reset will be available, as the progression system will be completely overhauled with Patch 2.0.
"While you'll be able to continue the game with your current character on an existing save, we recommend starting a new game after Cyberpunk 2077 Update 2.0. Due to the number of changes, starting fresh will enhance your overall gameplay experience," wrote the team.