Read about BT LE Audio. It offers one-to-many broadcasting including from your own phone to others. Also a venue can have numerous one-to-many streams, e.g., an airport streaming announcements in different languages. Just like classic BT, the standard should be universally implemented but it will take time for it to be widely available. Since the cost of installation is far less than t-coil and it is far more versatile, it should make t-coil obsolete but old habits die hard. The big catch is will HA OEM’s continue to make proprietary accesories or will they make accessories interoperable by adopting BT LE Audio for those as well???
BT LE Audio should go bigtime because of wearables, e.g., Apple AirPods, but we HA wearers will amply share in the derived benefits.