So here is my theory and have been saying it for a month. A deal was struck at the “Tarmac meeting” . Bill informed Lynch that Hillary is extremely ill, maybe even terminal, she will make a sympathetic figure and a prosecution would be impossible. The DEMS powers that be are making decisions, give us time.
That's a plausible theory.
I'd go a step or two further.
Hillary (and Bill, and maybe Chelsea also) are in mortal fear of Trump and what he could unleash on the Clinton Crime Family should he become President.
Hillary's use of a private email server and the fallout over her lax security practices is, IMHO, the tip of a rather large iceberg.
The email controversy is more than a distraction but less criminal than the much more significant--because of its size, scope and special tax treatment--Clinton Foundation, which the Obama administration won't touch but Trump could very well (if he really wants to clean house) pick to pieces with continuous investigations if elected President.
Hill & Bill could share a cell at Allentown.
My money is on Hillary staying in until the bitter end--which it may be if her illness is something more serious than treatable pneumonia.
She has too much at risk to drop out.