I'm aware of the How do I upgrade to the development release (aka. Ubuntu+1)? question and this is NOT a duplicate.
On my laptop running Ubuntu 12.10, when running
sudo update-manager -d, I'm getting "The software on this computer is up to date".
sudo do-release-upgrade -d starts the upgrade procedure
Is it a (temporary) bug in Update Manager which is going to be fixed or is it a change which makes our "canonical" answer obsolete? Or am I doing something wrong?