He's been under scrutiny since the original verdict though, esp. from the conservatives. The only thing I could see finally getting to him were the reports that talked about how morale within' the FBI has dropped & Comey was facing aggression from agents who wanted to reveal everything about what they found back in the original investigation (I can't imagine the reports talking about the wife of an agent receiving $500,000 from a Clinton ally has helped). I don't know if he will be fired, just that a few news shows today believed this is Comey trying to keep his job by doing, as you say, reclaiming the integrity. I don't think much is going to come of this however, as it looks like there are only a few e-mails the FBI seems to investigating that relate back to Clinton.
I'd suspect if anything will really put a blow to Hillary, it will be WikiLeaks dropping a bombshell. Kimdotcom claims he had found a legal way to access the 33,000 e-mails and had sent them to Assange for review, citing a Nov. 1-2 release. Kimdotcom is a rather unpredictable source admittedly, so it's still on Assange if he has any major evidence. His current crop coming from Podesta has only made headlines with the discussions of how to use Eric Garner's death in their campaign, which has upset his family.