I wanted to add my voice to the people asking for native IPv6 support. I use it for work (part of my job is troubleshooting problems on IPv6 websites); I have HE tunnelbroker.net set up as a workaround, but native would be much simpler. If there is any sort of beta testing, I would be glad to participate.
Also, the Member Tools > Labs > IPv6 Tunnels > View/Request Tunnel has returned "Function unavailable at this time. Please try again later." for at least a couple of months. :-(
By the way, I'm sure that Sonic is worried about the extra support load from IPv6 native customers. Although there is inevitably some of that during configuration, I have found that IPv6 server connectivity is widespread enough now, and the https://en.wikipedia.org/wiki/Happy_Eyeballs
client algorithm is widespread enough now, that ISP connections offering native dual stack are more likely to work then pure IPv4 connections. For example, Netflix tries to use both IPv6 and IPv4, so if there's an IPv4 problem caused by routing issues between the ISP and Netflix but under the control of neither, there still a good chance that it will work via IPv6 instead, leading to fewer complaints to the ISP. Put another way, native dual stack IPv6 should reduce "I can't watch Netflix" and "I can't connect to website X" type of complaints for an ISP like Sonic.