Will even modded saves continue to be compatible? I think I know the answer, but it would be nice to have confirmation. Since I am guessing the answer is maybe but there is no guarantee/mods will need to be updated for this patch as they normally do (especially UI mods which many other mods even console mods rely on), it would be nice/essential to have a patch 7 branch so people can keep playing while mods are updated.
Just like previous patches, there isn't a sure way of knowing the answer to this. If you are using hundreds of outdated mods, your save will potentially not be useable.
If you are using a few of the latest from nexus, or Mod.IO, your save will probably be fine, but either way it never hurts to be on a fresh new save.
They will drop another update at some point in December with updates to the "Stress Test", so if you have playthroughs you want to finish, you have time!