IMO Biden will enter if the FBI investigation is being done fairly and objectively. No doubt Obama and Biden are following closely what is happening. Will the DOJ try to kill the public disclosure of the FBI investigation or alter its findings?
And then there is Hillary's appearance before the Benghazi committee in late October. What happens there will influence Biden's decision as well. I don't think the Dem establishment wants Bernie the self-proclaimed socialist as the nominee.
Biden is waiting to see if a vacuum occurs. The first Dem debate is Oct 13, I believe, which means Biden will probably miss it.
I think toying with hillary’s candidacy is a tightrope for the Chicago regime. They have to be good enough to derail her yet not step in to the mine field that is mostly their making especially the mid east.