That’s a question people have been asking about MacBooks for quite a while now. If a 5G modem does come to a Mac, I don’t think you’ll see it on a budget Mac like a Neo -- probably a premium feature on a MacBook Pro or something.
I agree it would be a killer feature, but for whatever reason Apple seems to think only iPads and iPhones need mobile data modems ¯\_(ツ)_/¯