Never there are just a lot of people who die at opportune times and save their bacon.

Yes but unless it was blanket immunity she can be exposed for new crimes or if the FBI determined she lied they can revoke it.
As someone else noted Weiner is a real wild card in all of this. He could bring them all down to save his ass.

So you're saying there's a chance.

Bring them all down for what? Have they even said what this is about?

Who knows? I'm speculating but he likely knows just about everything Huma does. It doesn't need to be about this latest find. He can implicate HRC in any illegal activity she's been involved in...pay for play, emails, who knows. That's one way prosecutors make cases they get a small fry top spout and harpoon the whale (HRC).
As I said pure speculation but he is a serious liability if HRC has anything she can be indicated or convicted on.

Any odds on if he ends up shooting himself in tha back of the head?

Or electrocute himself taking a selfie of his weiner