The best you can physically do is about 2 ms more lag than the fastest ground based system, and that's assuming you're only adding in the transit time from ground station -> satellite -> user.
So it possibly won't be a killer for video conferencing, but keep in mind that the USAF's current system for drone video has 2 seconds of one-way lag. There's three orders of magnitude between what we're currently doing and the physical limit.
SpaceX's system will undoubtedly be better than what is in use today, but even with two orders of magnitude improvement (a HUGE improvement) you're looking at adding 20 ms of lag on top of what you'd already have.
So it possibly won't be a killer for video conferencing, but keep in mind that the USAF's current system for drone video has 2 seconds of one-way lag. There's three orders of magnitude between what we're currently doing and the physical limit.
SpaceX's system will undoubtedly be better than what is in use today, but even with two orders of magnitude improvement (a HUGE improvement) you're looking at adding 20 ms of lag on top of what you'd already have.