What does moving on look like? My guess is reassigning moderators of popular subs to big-corp sympathizers. Or maybe making the private feature a paid one (my personal favorite because it's a little petty). But it could be as organic as users making clones of the popular subreddits.
If you look to Digg vs Reddit-- Digg fundamentally changed the experience of a lot of users in an in your face sort of way. The Reddit changes may make it a fundamentally different platform now, but for the vast majority of users, they won't notice.