He's made it pretty clear that he "will do whatever it takes to stop Donald Trump" (or something along those lines), so I would react with incredulity if he spurns Hillary like that. I think it's more likely he'll make a tepid endorsement for her during his concession speech after the CA primary, as well as his convention speech, but will mostly campaign against Trump in the general, rather than for her.
Agreed. I think we'll see Bernie's focus on being anti-Trump rather than pro-Clinton. But he's not interested in telling his supporters to vote third party -- not gonna happen.