Eh, the islamic state and the likes of them dont need a bitcoin. They allready have the islamic informal banking system, which is basically - "I entrust you this money, my cousin in this or that place can withdraw that money from your family"
https://en.wikipedia.org/wiki/Hawala
Its very hard to track and certainly non-human SIGINT proof. If anyone on the planet wants those guys to pick up a systematic trackable crypto-currency, its the secrect services.