I’d rather not see this until after the Ds convention. The sooner they force Hilary out the more time Biden has to organize and raise money. If she totally tanks vs Trump by California she’ll come up with an excuse (health, legal issues caused by the VRWC, stupid voters) and give up. It won’t be her choice but the Ds can’t afford to have her at the top of the ballot if Trump becomes more likable and she keeps falling.
On the plus side it gives Trump more time to show what a fool Biden is. If Biden could jump in the day of the vote (not possible) a lot of people would think of him as a savior to protect them from Trump/Hilary and he’d have a good chance. A month of Trump tweets and news will undo a lot of that.
Hillary cannot win the nomination without the support of the Superdelegates. If they drop their support in favor of Bernie or Biden or both then she is a goner.
That could happen. It's Obama's Plan B.