Hey SethT,
As @Luke mentioned above inventoryItem has been added - so hopefully you’re unblocked fully.
For public apps (on the Shopify App Store) the deadline for migration is Feb 1st, and for custom apps (not on the App Store), the deadline is April 1st.
If you don’t migrate by this time, the apps won’t “break” but merchants who start using the increased variants feature, won’t be able to use it in the context of the app - and they’ll see warnings on their admin about your app. More info on this here: New GraphQL product APIs and early access to 2048 (aka 2K) variants