There are large ISP's that already have for the most part gone ipv6-only. Here's T-Mobile USA's roadmap: http://www.rmv6tf.org/wp-content/uploads/2017/04/04-IPv6-NAv...
Apple has already required all apps to support ipv6-only on iOS for some time. I think it's going to be a lot less rocky than you think.
There are large ISP's that already have for the most part gone ipv6-only. Here's T-Mobile USA's roadmap: http://www.rmv6tf.org/wp-content/uploads/2017/04/04-IPv6-NAv...
Apple has already required all apps to support ipv6-only on iOS for some time. I think it's going to be a lot less rocky than you think.