13.04do-release-upgrademotdupgrade
This was an issue with moving to 12.10 it appears to have resurfaced now with 13.04 i.e. post upgrade to 13.04 you still get the MOTD to upgrade.
I've tried the previous list of fixes for the same issue re move to 12.10 https://askubuntu.com/questions/253844/upgrade-12-04-2-lts-to-12-10-do-release-upgrade-fails-no-new-release-found but they don't seem to work, i.e. there is no /var/lib/update-notifier/release-upgrade-available to remove.
Please do not use do-release-upgrade to upgrade Ubuntu. It tends to break the system. Please use the Update Manager:
Press the super key (Windows key) to open the Dash, type Update Manager.
Hit the Check button then Install Updates, repeat the process until no updates is pending.
Press now the Upgrade button.
You will be alerted with the releases notes, Hit upgrade again.
Follow the in-screens instructions.
I believe you have problems of dependencies and whatnot, is such cases run sudo apt-get -f install to fix such issues.
Best Answer
I just "touch" the file /var/lib/ubuntu-release-upgrader/release-upgrade-available
But don't know why this file will not refresh automatically.