Development of Creative Commons licenses

[Harlan Lieberman-Berg <sysadmin AT tacticalbusinesspartners.com>]

One thing that I have noticed about the Creative Commons licences in
general is that they seem to have no potential to upgrade.  For example,
GPL has a statement that you can put in front of the licence to allow it
to be upgraded to any future version.  But, CC has no such statement in
any of it's licences.  Now, as far as I know, the only way to upgrade a
licence would be to get permission from all users who have made edits.
In some circumstances, with some works, this would be less complicated.
However, for a wiki setting, or other high-edit works, this is nearly
impossible.  

Am I missing something, or....?

Harlan Lieberman-Berg