Yes, however once they demod everyone, they will find other mods willing to do the work. There are a lot of people on reddit, something like 500 million monthly active users, at least some of them would be able to mod subreddits.
The other part of my prediction is that some of the (real, non-bot) engagement that the giant generic subreddits get are from users that are anchored to Reddit by more specialized subreddits, like those for specific games, hobbies, that sort of thing. If those special interest subreddits die out, I think the large generic subreddits will become more hollowed out than they are already, and not worth much.