Hi dogsittter,
and welcome to this Apple (user-to-user) Community.
Re: ReSound Nexia Hearing Aids with MFI and Auracast
Am no expert in this area, yet your post inviting comments deserves some response.
_____________________________________________________
Re: Will be receiving Resound Nexia hearing aids in two weeks.
Noticed that the Aids are listed with an asterisk (*) in Apple's List of Made for iPhone hearing devices - Apple Support The * signifies that the Aids use bidirectional streaming which allows them to be used with recent model Apple computers (those listed at the bottom of the article), as well as Vision Pro using visionOS 1 or later, iPhone and iPad. Yet, perhaps you knew that already.
_____________________________________________________________________________
Re: "My plan is to connect them with my Apple devices over MFI, and totally avoid pairing them using Bluetooth Classic".
If you haven't seen it already:
Apple support's online article Use Made for iPhone hearing devices - Apple Support
provides the steps for how to connect to the various Apple devices.
_____________________________________________________________________________
Re: "I already have several AURACAST streams which I will select with the ReSound Smart 3D App. I am hopeful that Apple will soon add Auracast support natively, so I can manage streams without needing Smart 3D or other third party apps".
Apple devices stream audio from phone calls, music, movies, podcasts, Siri, and more.
All rumours and speculation are outside the community's guidelines, so checking the Apple Newsroom for any relevant official announcements from Apple may be the way to go. (Today: received "no results" from a newsroom search for Auracast).
Seems Apple provides ample documentation and guidance for app-developers to keep ahead of any new improvements, and to ensure apps remain OS compatible.
All the best :-)