How will people upgrade from 12.10 to later releases after 13.04 is EOL?

Solution 1:

Yes, just as upgrades from LTS to LTS are supported, upgrades from an intermediate release to the next LTS are supported.

Historically this is only supported by manually changing your apt sources, since update-manager / do-release-upgrade require you to go step by step.

But since 13.04 will go end of life before 12.10, we will need to skip over 13.04 in the upgrade path. This will be implemented on the server (and with an SRU of the update-manager package to 12.10) to show the direct upgrade as an available option.