I don`t know if he would endorse Hillary. They have very different world views. To be honest I think a lot is owed to Bernie this election cycle, first of all for making `socialist`not so much of a dirty word. Second of all, getting more people involved in politics. And lastly, being able to call out the corruption in government. I mean even if you are a diehard Hillary fan, you cannot deny there is corruption on some level.
1) Socialist is still a dirty word, no one has really even bothered going after him for it because Clinton can't afford to look negative because people already think she's Lucifer incarnate for various reasons that are mostly ridiculous.
Fact is Sanders couldn't properly defend the term or the ideals against a question Univision asked about the failure of socialist states in Latin American. He completely side stepped it and had no answer, or if he did he chose not to give it because it'd be bad on the news cycle, which proves either wya that the word is still very much a dirty word (which is unfortunate)
2) Voter turn out is down, not up, Clinton last time I checked was on pace to match her popular vote totals from 08, whereas Sanders is several million behind not just Clinton of 16 but Clinton of 08 as well.
3) Calling out corruption in government becomes fucking meaningless when you yell it every time Clinton wins a fucking State.