Missing CC License - CC-By->2@ (full c for 2 years, then CC-BY??)

I was talking with Stian the other day about some amateur filmmakers who were hesitant to post their stuff as CC...and how many filmmakers make their $$ in the first year or two after release, and then their films disappear into oblivion. And how this is a shame for artists from smaller countries, like Norway, who's work is heavily subsidized by the public.

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...).