I'm in Ubuntu 14.04 LTS, and I've enabled the "notify me for every new release" option. I still am not able to upgrade through software updater.
Ubuntu 14.10 "Utopic Unicorn" hasn't been released. Check this website until it updates then download it. So excited :P
EDIT: It's released!! Check under Ubuntu 14.04 on that website :P
You should install all the updates for your current release from the Update Center, then it will promote about the new release.
If it still doesn't show up go to 'Settings' and under 'Software & Updates' click the 'Updates' tab and for 'Notify me of a new Ubuntu version'' make sure it's set to 'For any new version', click ok and check for updates and it should be there.