I'm perusing the schedules for 2013 and 2014. The 2014 schedule definitively lists two bye weeks, even with two open dates still to be filled. It appears the 2013 schedule would include two bye weeks if the final non-conference opponent is slotted into the August 31 open date.
I don't like this. I wait all year for Michigan football. One bye week is all I can take once they start playing. I don't remember two bye weeks in any previous season, but I haven't done an exhaustive analysis.