Hillary's negatives are too high and her health is still bad. If she has to testify about the email server, she'll do it from a walker. I can't see 77 year-old Biden choosing Hillary. That ticket would be too old.
@Restored She is NEVER going to actually testify. For one thing,as a VP (or President,after Slow Joe is forced out) she is just going to refuse and there is nothing that can or will be done about it.
By the time she is out of office IF ELECTED,she will either have the charges dismissed by judges she appointed while president,or will get the charges kicked because witnesses have died or withdraw their testimony,too much time has passed,or some other legal maneuver. Hell,she might even pardon herself! After all,who is going to stop her if she is the President?