At this point any warrant signed by Comey, McCabe, Page, Struck, Ohr or anyone else who swore an affidavit on this matter is now subject to review. A lot of criminal convictions are going to be overturned if their convictions were obtained by evidence obtained by any of these crooked cops.
Comey is a big one. If he signed this FISA warrant, he was playing a dirty double or triple game. Assuming McCabe's testimony about the dossier being necessary for the warrant; the fact that the FBI knew or should have known who paid for it; that it was hand-delivered by McCain, and knowing it was unverified makes Comey's actions very suspicious.
Then Comey briefs his new boss, Trump, on the dossier contents when he comes in; tells him that there is no investigation or suspicion of Trump's dealings with Russia, and at the same time refuses to say that publicly, while knowing all the surveillance that took place on the basis of a suspect FISA warrant. Then, when he is fired, he leaks through a friend (now claiming attorney/client privilege) hoping to get his other friend Mueller, appointed by another long-time associate, Rosenstein, to go after Trump. A treacherous, double dealing bastard. He even tried to play it both ways by pretending to investigate the Hillary emails on Weiner's computer. And he's teaching ethics!