You can run 500ms live with HLS buffering -- that is being done now by many webcam sites... where have you been? Video and sound out only.
WebRTC video conferencing software is available. Has been for a year now. Problem is that a limited number (5-7 people) can video conference at once -- cams and voices on. Also, there is a location issue that relates to the connection latency -- different continents or even land mileage.
Put one cam on home based fiber pipe of 1G and quite a few could connect to 'her' in silence. We did an experiment with 28 people 6 months ago and this worked ALPHA (buggy).
Last night, I tested 2/1.5 Mbs upload and1/ 4G upload with 3 cams Linux and Android (windows works fine in Chrome) for 2.5 hours video+voice in Chrome -- worked fine. Safari needs to "adapt or die"
Is WebRTC ready yet? Take Safari off that chart WebRTC 90% ready to go. iOs can degrade to view only native HLS for now. If your auto is too old to use E85 ( flex fuel) -- unleaded is still available.
Periscope is using HLS (still?) and linking over 1000 to a broadcast sometimes. Generally, less than one hundred with no noticeable latency if the broadcaster is connected to WiFi -- 3G or 4G is another story but 5G is on its way and there will be other bandwidth enhancements. With 4G there are connectivity issues related to tower range and device movement ( like in a moving vehicle ).
Perfection and feature creep just retards progress with methods and business models obsoleting much faster today than they did 5 or 10 years ago. The problem is not the perfection of the technology -- the problem is people adapting to the new methods and technologies.