Android 12 / API-31 support is already available in Visual Studio.
There are some caveats for using this in Visual Studio 2019 as use of JDK-11 will prevent other features from working. See https://github.com/xamarin/xamarin-android/wiki/JDK-11-Warning for details.
In general, https://github.com/xamarin/xamarin-android is a more appropriate place to ask about future features and roadmaps and to report bugs. Q&A is a good place to discuss and to ask for help on what already exists.
--Rob