Much as I'd like to see a senator Amash, it will be very tough, and I'm not sure the risk is worth the reward. I don't think it's impossible. The Dems have a thin bench, and most of their big names are pretty old. And in a 2010 sort of environment, I think he would win, and the midterms of a second term president are almost always bad for the party in the whitehouse. That said, Obama remains reasonably popular, and it's hard to say if 2014 will have the sort of populist anger that would be needed to make a bluestate like Michigan competitive.
Not sure if this was posted, but PPP tweeted that Levin was beating Amash by 15 points. That's pretty decent I think, considering how long term Levin had been there. If we assume that any new Dem would not do that well, it's probably reasonably a single digit race. But making it competitive and winning are two different things. My advice to Representative Amash is to wait a few months, see what the fields look like, do some private polling, and see if this is a race that he can win. If it's not, it's better for him not to make the jump.