From all that I've read, the young Bernie fans are behind him regardless of party affiliation. It's Bernie and his ideals they align with. So it's possible they could vote for Trump, but it's also possible that I have ocean front property to sell in Iowa. Some will vote for Trump, but if Bernie does his duty and advocates that he and Hillary have more in common than not, Bernie's Bros and Sisters will come around to Hillary by 75%. (An estimate I read.)
My FB feed is full of items from otherwise reasonable friends who post "memes" saying things like "Trump and Hillary are on the same side." It's quite disconcerting.