When you see in your timeline a discussion between lead dev of three major project of the #xmpp ecosystem, you can be sure that this federated network is on the good way
@alienghic
Nearly all clients are connected via ipv6 on my server, but you can never be sure, people can use a stupid wifi etc. So it's good to have a turn server just in case.
My Alditalk mobile contract gives me ipv6 @daniel
Some in my family had ipv6 not enabled in the APN settings. I turned it on then then it just worked. Don't know why it isn't always the default.
Monal said they had a fallback TURN server which wasn't getting used enough for them to get billed extra.
I had a hunch that ipv6 connectivity is probably reducing the chances of needing a TURN server, but its probably not always going to work
Probably thee best way of answering this question is with server logging and just tracking how many calls are being generated and how often STUN or TURN get used by protocol type.
@adele In an XMPP room I admin, I looked at the JID's of the participants to see how federated the chat was. I was pleasantly surprised that the great majority of users didn't share a domain, so in fact it was very highly federated.