My app is using IDFV (id for vendor) and a third party analytics framework is using IDFA (id for advertising).
I'm not planning to upgrade my app using XCode 12 right now, but in the next few months.
What will happen for both identifiers if an user is using iOS 14 on my app built with XCode 11 and ios 13 SDK? permission will be granted by default or asked?
From what I understand:
On iOS 14 the IDFA is nullified until you get the user's authorization to use it, which means that you get zeroes if you don't ask, and you also get zeroes if you ask and the user refuses. If collecting the IDFA is really important to you you will have to use Xcode 12 to provide a version compiled with the iOS 14 SDK, ask for the authorization, and hope some people give you the authorization (but don't count on it).
IDFV will still works as of now.
edit: Apple just announced that they will delay the necessity to ask for the permission to use the IDFA. So you are saved for now.