> ... there aren't actually that many hurdles left. The biggest one is IPV6. Once that is pervasive, then you have an easy way to get end to end connectivity without having use a central server to carry the content...
On a side note, I don't believe it to be a major problem in this context though.
Almost all voip problems are lack of bandwidth and wifi lack of reliability. Enough BW and a wired connection and its as perfect as legacy copper wire telephone service. The bean counters are of the opinion that 95% reliability is spending "enough" and the popular science article writer are of the opinion 95% reliability is the same as 0% so this will not change until the economics and infrastructure of broadband connections dramatically change. The problem has nothing to do with app developers or library authors, and has everything to do with the network engineering team in IT fighting with the bean counters, on several levels.
The frustrating part is that none of this should be a problem. It's just that lots and lots of routers don't follow the specs properly. Here it is 2017 and you still can't reliably punch a hole in a firewall.