The chain will survive but the mainstream adoption will be gone, which is already nearly non-existent anyway. Some centralized semi-anonymous exchanges like eXch will offer solutions but for how long? Sooner or later they'll get targeted by the feds also. When they reach above a certain amount of activity, they will be the next target... Then another solution will emerge and they'll take it down too. It will be a hide and seek game like they do with torrent trackers.

The other option is bisq (a real decentralized solution) but bisq consumes too much CPU resources and it gets pretty heavy after using it a while. Maybe bisq will benefit from these take downs.