Apple (and the Swift project) uses available: 9999 and deprecated: 10000 to indicate availablility for future (unannounced) versions of OSes or Swift. It's likely they just haven't gotten around to properly updating the annotation for the now-announced iOS 14. You can report a bug but hopefully they have an automated checker for this stuff and the change just hasn't propagated to the betas yet.
deprecated: 10000 means "soft-deprecated", i.e. it's not deprecated now and will continue to function, but it's not recommended. It's the same value used in the API_TO_BE_DEPRECATED macro in availability.h.
Is there anyway to make Xcode show warning of these deprecated call? My Xcode 12 project deployment target is iOS 14. I want to see deprecation warning.
One temporary, mediocre solution I found was to open the Xcode project file (e.g. MyProject.xcodeproj/project.pbxproj) in a text editor and replace IPHONEOS_DEPLOYMENT_TARGET = 14.0; by IPHONEOS_DEPLOYMENT_TARGET = 100000.0; You'll get a lot of errors when you open the project in Xcode again (tested with Xcode 13.0) but also the deprecation warnings for the open SwiftUI files in the Xcode editor.