So I took a look at this table of unclaimed state super-delegates and brought out my spreadsheet.
I personally think it would be fair if a state's supers roughly broke out by the state's popular vote.
It's true that some states already far exceed that percentage (New York and Illinois, notably). There's no way the remaining supers in those states can make up for the percentage deficit, even if they all jump on the loser's side. So all you can do is collect the remainders.
That's what I did. I figured out what the equitable split would be for the supers, for all the states that have voted so far, excluding Michigan and Florida.. and Massachusetts, since the table was missing how many delegates are available. Then I allocated the remaining supers in a way that would come closest to approaching those percentages for each state.
Both candidates advantage depending on the state, but overall, Obama would make up the deficit a bit, by gaining on Clinton by the amount of (drumroll).... 38 superdelegates. Meaning, the superdelegate margin Clinton has over Obama would shrink by 38.