This is a perfect example of one of the Freedoms we don't have with web applications. Even with Microsoft Office you have the freedom to keep using the software today in the way you did yesterday.
Even open source web applications don't have this freedom... If wordpress.org were to do this, those users would be in the same boat.
I've been working on an open source infrastructure project to fix these issue for a while, but it's still pretty nascent. My "manifesto" on that is here: http://bit.ly/forkolator