I personally expect Sheffield to return during the Rumble. No idea on Tarver though.
The last I heard about Sheffield was that he was still on crutches and that was back in November I believe. A compound fracture is a serious injury to come back from. I don't see him returning until the Nexus is long over which would be sometime late spring or early summer.I've read in a few different reports that he was due back "late 2010-early 2011". That's where I got the idea for the Rumble.