Here is a link to the Cavs salary cap projections for the next few years. The 2014-2015 cap is $63.2 million so
Cleveland is more than $16 million under for the next season (not including Wiggins deal). They could offer Luol Deng $12 million or Spencer Hawes $5-$6 million to bring back their two free agents. But it is unlikely they could bring back both.
Here is their depth chart in order of minutes played last season:
Backcourt - Irving, Jack, Waiters, Delladova, Gee, Wiggins
Frontcourt - Thompson, Varajao, Deng, Zeller, Hawes, Bennett
If they can use Varajao's expiring as trade bait and package Waiters (personality dump) and Jack (salary dump), they could free themselves up to do something interesting. But without a move, or without bring back Deng, these Cavs will be in the 25-35 win range again. Otherwise they may have to wait for Wiggins and Irving to mature as players and hope to land a big man to replace Varajao's production.