It won’t be Hillary. I agree. I think it will be post-convention and nomination. Her VP choice will become the nominee. She will select Sanders as VP. Trump will be competing against Warren/Sanders.
I disagree. If they don’t pick someone else at the convention, no way will she step down, even if she’s indicted. Not that she will be, even if the FBI recommends it. And once she has the nomination, what mechanism is there for the party to force her to? It’s now or never, and she’s all in no matter what.
13 weeks post convention to election is not enough time for them to put on any resemblance of a campaign.