In my Android and iOS apps I’m using in_app purchase to unlock app content. Now I want to move to a third-party payment system (Braintree) that integrates with a web version of the app, and move from one-time payment to subscription (subscription will apply to an account that can be used cross-platform, and so can be used more widely than just in the app itself). However, I still need to use the old in-app purchase code to check for those users that purchased by the legacy method (those purchases will still be valid). My concern is that we are using the Google Play/App Store in-app purchase code, but without allowing new purchases using that method. Do you think we will run into issues due to this?
No it won’t get any problem, you can check Netflix & Spotify are also doing same