The best way to make 6to4 diminish has always been and still remains:
Deploy Native IPv6 Now.
That's a plan and a necessity at this point, but, execution is still somewhat lagging.
Of course, Comcast *is* deploying native IPv6; see, for example, http://mailman.nanog.org/pipermail/nanog/2011-January/031624.html It just takes a while -- and a non-trivial number of zorkmids -- to do things like replacing all of the non-v6 CPE.
--Steve Bellovin, https://www.cs.columbia.edu/~smb
Comcast was not the target of my comment... The networks saying Comcast shouldn't help the rest of the net by providing open 6to4 relays were the ones I was referring to. I again applaud Comcast's leadership on IPv6 to the end user, even if they haven't gotten it to me yet. ;-) Owen