will apple offer true Family Sharing for Apple Photos like Amazon Photos Family Vault?

We are all users here. We don't know what Apple will do in the future until Apple announces it.

If you have specific needs that you want to request that Apple address, use their formal feedback mechanism: https://www.apple.com/feedback/

That would be nice, yes. That is what Apple offered for a limited time for iPhoto, over the local network. Apple stopped it, when iCloud came out, without any replacement.

It would be nice though to be able to read only view my Wife's full library, and for her to be able to do the same with mine, via iCloud family sharing.

Apple has never offered to share a Photo library with any photo application, since iPhoto came out in 2002. For a short time we could browse each others iPhoto libraries on our local network, but that feature has been removed again.

Based on my experiences with a shared photo library it is much safer to have a private photo library and just to share selected photos, exactly, what Apple is offering. I have tried several times to share a photo library with others ( for ongoing research projects) and there have always been problems with users who dumped thousands of photos into the shared library without weeding them out or tagging them correctly, deleting photos shared by others without ensuring there were backup copies, adding funny comments and edits. You can only share library with disciplined, responsible partners who know what they are doing. I am glad that Apple only offers to share selected photos and not the library. This way I can refuse the access to my Photos Library, simply because it is not possible and I have not to tell the people who are asking "Sorry, I do not trust you not to mess up my library". I am sharing photos by sharing copies of the best photos, so others can add the photos they want to keep to their own library.