Apple has stated that "App updates must be built with the iOS 13 SDK starting June 30, 2020" . See the section 'Build with Xcode 11' from here.
Though it will be breaking change, but I think we can drop it before (probably in 9.2.0) because -
1. As per apple's statement, I think no one will be using Xcode < 11.
2. XCFramework is supported in XCdoe 11+, which we require to completely fix
3. MacCatalyst is supported in Xcode 11+, which is required for