If an indictment happens ( I think it’s a big If) it will come after Hillary does poorly in the first couple of states. If Bernie is surging, the Democrats will toss Hillary to the wolves and bring in Biden.
I also thought that scenario will play out but I think they waited too long. If Bernie smashes Shrillary in Iowa and then New Hampshire, I think his momentum will be hard to stop. Inserting Biden at that point might be too late. Like with Trump, it will be too late to put that genie back in the bottle.