This is actually an interesting point that I have wondered about occasionally.
The salary cap is expected to fall in summer 2010 and depending on where it comes in, once LeBron resigns, the Cavs will have some capspace, but it might be less than the MLE. The MLE will likely decline a bit as well. For the sake of the argument, what if the Cavs have $5m of capspace left after LeBron resigns, but the MLE is calculated as $5.5m? Could the Cavs use the $5m in cap space and then use the MLE? Otherwise, the Cavs would be operating at a disadvantage. This is assuming the Cavs aren't resigning Shaq (or Z), of course, and if they do, then this is a moot point -- they will be over the cap and will have the MLE to work with. And it is also moot if the Cavs trade Z for a mulit-year salary commitment. It's also interesting to note, in the current context, if the Cavs trade, say, Jawad and Coby for Jason Smith, the $5m or so they would have in capspace would shrink to $3m...
My conclusion, which is hardly earth-shattering but still interesting...Based on their interest in converting their non-guaranteed contracts into another player, possibly with a multi-year contract, the Cavs are intending either (1) to resign Shaq (or Z); or (2) to trade Z.
In any event, the Cavs are clearly expecting to be over the salary cap at the end of the season after the contracts of Shaq and Z are off the books.