They have plenty of unreleased material if they want to put out another boxset. Back in 2010, Obie said that while he was searching the vaults for the live songs to be included in the Special Editions he found 25/30 demos they completely forgot about. The thing is, Island/Universal is not willing to invest a lot of money in a project that only diehard fans will buy.. But still, they could release it only on the digital stores in order to reduce the costs a lot...

About Cadillac Man, I remember an interview where Jon said they never recorded a proper studio version of the song. Could be wrong though.