Some assumptions would be:
1. Use of the fastest available hardware.
2. server dedicated to hosting one single large meeting
3. a very small group of hosts and presenters would share video, audio, plus a presentation.
4. all remaining participants are viewers and are not sharing video, audio, etc.
5. streaming is not an option, all participants must be real time.
6. enough internet bandwidth is available to host the meeting.
If there is no path currently to get to 1000 participants then any hypothetical discussions of how to theoretically get to 1000 are welcome.
Any thoughts or input appreciated.