It is no secret that President Putin has used the tactic of using assassins to kill his rivals, however the fact that this ex spy has come to light frequently in the media, it is very unlikely that Putin will have him killed, and he certainly wouldn't get away with it. I say that Putin would be the one to have him killed because I don't see any way the Americans would have the skill and knowledge to complete a high target assassination over seas. We have seen in the past the Russians assassinate targets in the UK, however I feel that as of now, the spy is safe, for as long as he stays in the UK that is...
No, the British ex-spy that wrote the latest dossier about Donald Trump's involvement with watersports and the Russian government is not safe. Hey may not be in danger directly from Donald Trump, but he should be concerned that the person who put Trump in power, Vladimir Putin, would want him dead.
No, the spy who exposed Trump for the fraud, liar, cheat, and depraved man that he is isn't safe at this time. He needs to go into hiding and change his identity, much like somebody in the witness protection program would have to do. This ex-British spy needs to take measures to protect himself immediately.
No, neither he nor his family is safe because the dossier was about a very important person, Mr. Trump, President elected of the United States, who is maybe the most powerful person in the world, and also the Kremlin, Russia's power. If either one wants to go deeper in the investigations,he better watch his back.
Part of the spying profession is the risk of exposure. An exposed spy is never safe because they have been privy to many confidential activities and whether the Trump dossier is relevant or not, this man may be abducted and interrogated simply on the off chance that he knows something. If he does, indeed, know something, his own agency may have to take action against him.