Both of the above points make sense, as the takeover of Litchfield didn’t really involve Piper, and you can’t really have inmates running amok with the brutal guards of Season 4 running around.
That doesn’t seem like it would end well for any group of inmates, but Orange Is The New Black’s Litchfield has always seemed a little laxer than some actual prisons.
Judging from the media attention and flashing cameras, it’s my guess that the prisoners have the guards on lockdown.
It does ask the question about where exactly all these employees went, and whether or not they’re even out of the prison.