Ubisoft is continuing to go back and patch older Assassin's Creed games, after Syndicate recently got a 60fps patch and resolution boost on consoles the next one up is the popular AC4 Black Flag, for now the Steam version has been patched to add in Achievements and proper banners/artwork in the Steam UI.
Proof that it's retroactive but you'll need to launch the game to get them which means they all appear as very rare:
Eyes should be on the console versions next to see if a patch appears on them soon hopefully giving it the same res boost and 60fps treatment.
Achievements Added to Assassin's Creed IV Black Flag! :: Assassin's Creed IV Black Flag Events & Announcements
View full event information here: https://steamcommunity.com/ogg/242050/announcements/detail/658185520169353387
steamcommunity.com
Proof that it's retroactive but you'll need to launch the game to get them which means they all appear as very rare:
Eyes should be on the console versions next to see if a patch appears on them soon hopefully giving it the same res boost and 60fps treatment.