Make your peace, cry, shout and scream now

With a reconfirmation that arcane will be canon and that stories will be subject to change if the writers feel it necessary, we are entering a second lore retcon period.

Considering how drastic changes were made with characters like Warick and Viktor, and how soft retcons like Caitlyn and Jinx were, I think it's safe to say that changes will range from slight tweaks and added depth, to complete back story changes