I have a feeling this could end up like Massachusetts - Clinton was supposed to romp there, and it ended up being very close. That said, I think she will have a decisive win, at least 52 to 48.
RCP's average in Massachusets was Clinton +6.7, it was off by about 5 points.
RCP's average in Michigan is Clinton +21.4. There's no comparison.
The reason a lot of people though MA was going to be a blowout was because it seemed like Clinton had momentum. Later polls were more favorable to her than earlier ones, and Clinton had just won huge in SC. In hindsight, constructing momentum narratives out of just a few polls turned out not to be that accurate.