Sane path to distribution upgrades
No. You should never just edit sources.list. Use the update-manager, or if you use command line, use do-release-upgrade. You can upgrade safely from LTS editions to other LTS editions, or otherwise, you need to step via each release. Only those pathways are supported, and prevent some issues that can otherwise occur with improper upgrades.
I believe you can upgrade directly from LTS to LTS, see e.g. https://help.ubuntu.com/community/LucidUpgrades