Here's a great post on how to react and even thrive if Apple rolls out a feature that copies your app. There are six lessons that Astropad learned when Apple introduced Sidecar back in June. After the initial shock, the Astropad team got to work. It's not the end of their product, but the tough lessons they learned include thinking about cross-platform sooner and diversifying.
I would argue that these lessons are great for any app, even if you don't think you would ever be sherlocked.
What To Do When You Get Sherlocked By Apple by Savannah Reising