The developers of Assassin's Creed Black Flag Resynced have plans for post-release content: a "New Game+" mode, possible DLCs, and other changes are being discussed. Ubisoft is also considering adding the challenge system from Assassin's Creed Mirage.
Game director Richard Knight said in an interview that replaying missions with new conditions would be an "excellent idea." However, implementing such a feature will not be easy.
I can't promise anything just because it's in Mirage, but it's not in the current version of Anvil. These are new technologies. They have a solution, we roughly understand how it works, but it will take time to figure out if we can create it and how long it will take.
Knight also noted that he is interested in such a system due to his experience working on Hitman.
Personally, for me, as someone who used to work on Hitman and played it a lot, being able to see a speedrun timer on the screen is a very interesting way to play.
Ubisoft Singapore is still preparing a roadmap for Resynced. There is no release date yet for "New Game+" and other changes.