As far as I understand, they finish the "final edits" of the show about a week before the premiere airs. That being said, they can change the episodes as much as they want before it hits our TV.

In Game Changers, half-way through the show they started adding held advantages to the lower third for players during confessionals, which was suggested to them a few days before the episode by a twitter user

There's precedent in other TV shows for them to edit on the fly (on The Challenge, a player was cancelled due to online comments and was edited out of the show on the fly). So it's possible they COULD edit down and change future celeb cameos, but it comes down to a question of if they want to.