They will all resign before allowing Trump to fire them.
I would be a bit surprised if they did resign. I think they want the talking point of Trump firing people who were investigating him. Doesn't matter to the MSM and the leftists that the charges were bogus. It's the message that matters to them, not the facts.
Same goes for the illegals. Most will stay put or go to a "safer" state or city rather than self-deport. Given how many illegals there are in the country, they probably figure the odds are on their side of not being forced out, at least not right away. Self-deporting means having to deal with their country of origin, which will be worse than anything that might happen to them in the US. A fair number of them may go down swinging here in the states.
Refuse to accept their resignations and then fire them.