Ran full software update using software updater in 13.04. When I ran software updater again, it is showing system is fully updated and no option is displayed for upgrading to 13.10.
It is possible that normal upgrade notifications may have been disabled. Please check Softwares & Sources > Updates > Notify me of a new ubuntu version Select 'For any new version'. If it still doesn't work try this from the command line:
If this doesn't work either, you can post the output of the command for further looking into.