Yes, the life of ex-MI6 officer Christopher Steele is at risk as a result of the release of his dossier outlining the perverse sexual proclivities of U.S. president-elect Donald Trump and the ties he has to Russian oligarchs. Even if Donald Trump does not pose a risk, Vladimir Putin probably does.
Trump is a scary dude so it could be possible that Steele's life is in danger. The threat probably won't be directly from Trump but from his supporters. Trump makes a lot of promises and threats but doesn't follow through on them. It's his supporters that feel justified by his rhetoric that are the real threat and will follow through if they feel a need to.
Most people would not want to be in the shoes of former MI6 officer Christopher Steele, after Steele dumped a dossier on Trump allegations. Many of the allegations appear to be baseless and lack any evidence. However, Steele should be paranoid for crossing the president-elect. Steele might need to hide out for a while until the news story dies down.
The dossier includes unsubstantiated claims that Russians possess videos involving prostitutes, filmed during a 2013 visit by Trump to a luxury Moscow hotel for the Miss Universe contest, supposedly as a potential means for blackmail. It also alleges that Trump advisers including his lawyer Michael Cohen maintained regular contact with Russian officials and others linked to Russian intelligence during the election and have been exchanging information for “at least” eight years.