Man, if he went independent for the GE, I'd be sooooo conflicted. On one hand, the Dems have the best shot at beating the Republicans, but on the other hand, I'd feel internally obligated to vote for the candidate I most believe in. Bernie would not be an insignificant spoiler to Hillary if he ran independently. And beyond that, I would looooove for a viable far-left party to exist in American politics. I'd probably vote Dem if Trump got the Republican nomination, but if Trump were to also go third-party, Bernie all the way. I'm not loyal to the Democrats--only averse to the Republicans.
Can you imagine? A four-way GE between Hillary, Sanders, Trump, and whoever the Republicans put up? Two independents with sizable bases supporting them? I can't even imagine what that would be like. Fantasy scenario, but it's not completely outside the realm of possibility.