No. M.Hill was a junior, but you raise an interesting point: I assume that Williams and Clarett have aquired the service of agents. If the ruling is overturned on appeal, will they be allowed back to their teams? Probably not. This also makes me think that they're pretty sure that it won't get overturned.
If the ruling is overturned on appeal AND they're allowed back on their teams, would they even play? Both left on unpleasant terms.
Actually, this rule not being in the CBA is what allowed Clarett to enter the draft. The rule was set up by the NFL a while back and there was no fuss made over it. The actual rule itself was not included in the last CBA. Personally, I think they should do something similar to the baseball system. You have a chance to be drafted out of high school but once you enter college you are there for 3 years minimum. This would allow for super-humans like Lebron but would also protect college football. A system like this actually wouldn't be that bad for basketball too.