Fullback Stephen Hopkins has left the team, according to all of twitter. That's unexpected. Hopkins had some injury issues early this season and was on the verge of getting Wally Pipped by Joe Kerridge but had seemingly fought his way back to starting before a pretty terrible outing against Ohio State. Seems like that was a breaking point but that's just speculation.
With Paul Gyarmati graduating, that leaves Kerridge and freshman Sione Houma the main options at fullback, which is fine. Kerridge seemed to be a better blocker than Hopkins anyway. Houma has played on special teams for whatever reason and seems like more of a run/catch threat from the spot if and when he sees playing time. In addition to those two guys Michigan is also bringing in Khalid Hill and Wyatt Shallman as H-back sorts*, so they're fine at the spot.
Hopkins leaving opens up a 24th scholarship in the class, with more attrition pending. Given the flurry of offers Michigan has issued in the past few weeks it's clear they're looking for another linebacker, preferably a SAM type**, and I would guess they go above 25 if they find enough players they like.
*[FWIW I bet a dollar Shallman is on defense by the end of his freshman year.]
**[I don't think this has anything to do with Cam Gordon or Jake Ryan. It's more about the freshman class. If Royce Jenkins-Stone isn't going to be a SAM, and it doesn't look like he will, then there is no one younger than Ryan on the roster who can play the spot. Even if they make the logical move and slide Mario Ojemudia over, they could still use another guy there before Michael Ferns arrives in 2014.]