Google is working on a new version of Blogger which is now in beta according to a page hosted on blogger.com. Here's the full message:
Could not switch you to the new Blogger
Once the Blogger account is linked to the Google Account, users will be able to login using any of the credentials as you see in the screenshot above.
Another indication is this page which clearly says that you can signup for Blogger from a google account or link to an existing account.
Update: The service is live now. Stay tune for a detailed review.
Could not switch you to the new Blogger
Thanks for your interest in the new Blogger in beta! For now, we are only switching a limited number of users to this new version. We can't switch your account at this time, but hope to be able to do so soon.Tony Ruscoe has discovered that Google is selectively moving Blogger accounts to the Google Accounts (just like the integration of Orkut into Google Account service).
Once the Blogger account is linked to the Google Account, users will be able to login using any of the credentials as you see in the screenshot above.
Another indication is this page which clearly says that you can signup for Blogger from a google account or link to an existing account.
Update: The service is live now. Stay tune for a detailed review.