Hey Dibs - - in an older thread we discussed whether unused cap room could be "re-rolled." The discussion in this thread spurred me to google search the issue again, but I still can't find anything definitive.
I did have an additional thought, however. The provision of the 2011 CBA that allows rollover of unused cap room was designed to replace the commonly used gimmick of creating performance-based bonuses that temporarily counted against the cap in year 1, but when not actually earned the unpaid $$ would roll over and be added to the team's salary cap in year 2. Because there was no restriction on the ability to repeat the process with new gimmicky bonuses in year 2 as far as I know, the old system didn't result in any unused cap money from year 1 "evaporating" if it wasn't used in year 2.
If the new system was merely designed to simplify things, as seems likely, there shouldn't ever be any "evaporation" of unused year 1 cap money if it isn't spent in year 2 (assuming the team elects to use its option of electing to roll it over).
Certainly not definitive, but maybe the history of how the rollover option came to exist in the 2011 CBA gives more hope that unused cap money in year 1 doesn't simply "evaporate" if not spent in year 2.