IPv6 is useless for now on
IPv6 will be useful when there will be users who will connect to IPv6 only networks in native mode. It is not the case today and I don’t know if it will happen any. However, all the networks today are either IPv4 or dual stack (IPv4/Ipv6). There are some networks where people connect to the Internet thanks to an IPv6. However, these networks have a translation module to map IPv6 to IPv6 and vice versa. It is called NAT64. So let’s imagine an Internet Service provider with 500 millions of devices connecting to the Internet thanks to an IPv6, they will be able to connect to IPv4 only websites thanks to NAT. IPv6 could useful someday if the IPv4 gets so expensive so that new servers will only have an IPv6 in native mode. We can postpone this problem by allocating IPv4 addresses from clients to servers.
Very few websites support IPv6 in 2018
If Airbnb, Amazon, Ebay, and Walmart don’t support IPv6 why should you support IPv6?
IPv6 has no benefits for your website
IPv6 does not bring additional security, performance. It does not have any SEO benefits. It does not help to reach a new audience.