This made me think that it might be beneficial to have a CC license that can change over time. I.e. it is maybe a full copyright, or a restricted CC for a few years, and then becomes CC-BY. I assume that people can change their copyright on their works on their own over time - for example, something of mine that is now copyrighted, I could make into CC-BY when I want - but knowing me, I would have forgotten about the work by the time I wanted to do that.
Perhaps we need:
CC-BY->2@ (i.e. becomes CC-BY, after greater/longer than 2 years regular copyright - and one could change the 2 to whatever number...).