Just a quick PSA for all the modders out there valiantly updating their mods to 1.3.
There's no need to break compatibility with 1.2 while adding support for 1.3! It's quite easy to make a mod support multiple versions of the game, just by putting the old version's files in one folder and the new version's files in another.
If you want to be more efficient and share identical files between versions, you can do that too. You can even define your own custom folder structure for full control.
This document explains the details on how to do it: Multi-version mods in RimWorld[docs.google.com]