Even the final version of Ubuntu 14.10 is not available yet, we can easily upgrade to Ubuntu 14.10 from Ubuntu 14.04 with a few steps. This method works for Ubuntu 14.10 Final Beta or Release Candidate. I hope this method still valid for Ubuntu 14.10 final version. Canonical provides a straight-forward upgrade path, so it is quite easy to get Ubuntu 14.10 beta.
Steps to upgrade to Ubuntu 14.10 Beta from Ubuntu 14.04
Open Terminal and paste these commands
sudo apt-get update
sudo apt-get dist-upgrade
Now, after the system is up to date, we need to continue upgrading using this command
sudo apt-get install update-manager-core
sudo do-release-upgrade -d
Now reboot Ubuntu.