Apple's stated policy is that KPIs will be deprecated and removed as System-Extension-based alternatives become available. Given that the IOUserAudio* classes appear to replace IOAudioDevice, IOAudioStream, etc., should I assume that any kext with a com.apple.iokit.IOAudioFamily dependency may soon be prevented from loading?

Currently AppleUSBAudio is implemented as a kernel extension and uses the IOAudioFamily KPI. Given the new AudioDriverKit Driver Extension framework, having AppleUSBAudio as a subclassable AudioDriverKit would save a lot of effort for USB driver development. If AudioDriverKit is not sufficient to fully implement AppleUSBAudio then I'm assuming Apple still sees the need to continue use of IOAudioFamily and that it will continue to be available for use in kernel extensions.