My guess would be that it becomes just a flavor mod?

It dies

We will continue updating and make use of the new mechanics added by AUH while still using the same map projection we are using now.

Hey you don't need to completely abandon the mod. Many assets can be copied over & this mod still expands various regions in Asia already in the game, such as India.
You can take various adjustments, such as in Caucasia or the addition of Papua (which seems like it won't be in vanilla), "Stateless Governments" (great for groups that stay underdeveloped), the variety of religions in China & the Cannibal religions of the Malaysian isles (if Ck3 decides not to add them) are all great additions.
You could also transfer the clothing in this mod over to the updated game (even if it already adds similar clothes), therefore diversifying the appearance of the characters more.

Honestly this mod still has a lot of content the official update is missing (looking over at you phillipines)