I really like the idea of switching to multiple actively managed
maintained sage versions which is suggested somewhere in this thread.
I just happened to have suggested it also in a response to Williams
blog
http://389a.blogspot.com/2010/08/computational-projects-part-1.html.
Where he discusses the issue that there is a large gap between writing
code which gives you the result needed for your research and getting
it up to standard to get it into sage.
Somehow my reply is not jet visible there. But the main point I
suggested there is that there should be some sort of unstable branche
like in the debian development cycle:
http://www.debian.org/releases/
This unstable branch could be used as a central place to add all the
code used for people their own research which is meant to go into sage
at some point.