We know Stadia is adding achievements post-launch but what about the games which are launching before the achievement system has been added?  This is a question that needs to be answered as achievements matter to a large group of gamers. 

My hope is that there is some sort of achievement tracking system already in place for games so you don’t need to replay games in order to unlock the achievements. For example, when the achievement system is launched all games you have played achievements are unlocked automatically.  Some games like Assassins Creed Odyssey can be played for over 100 hours and missing out in achievements will disappoint a lot of gamers.