Isn't Cavill only training right now? It wouldn't be hard for him to fly out for a few days and film a small cameo. Not saying it's true but it's not impossible..Cavill is filming The Witcher in Europe when they're doing those reshoots.
It's not that at all. June is a much better date for it. WB previously had the Six Billion Dollar Man in June 2020. They moved that movie off the date, and put Wonder Woman in the better release date. They can make an additional $100-200M there as opposed to the crowded November. They also have Joker in October 2019 so this spreads things out better.
Let me dream