I believe the folks worrying about IPv6 only are just looking ahead to a possible future. Especially when they are looking at the question of do all the pieces work locally, vs do popular domains support it.
There are domains like T-mobile US that are IPv6 only already. T-mobile runs NAT in the network so that all of IPv4 is NAT'd to IPv6.
I do think it is reasonable to expect there will become a time when IPv6 is pervasive enough, that new deployments will target users with IPv6 rather than IPv4.
Once IPv6 becomes the choice to support to get new customers, it is reasonable to expect that IPv4 support will start deteriorating and will eventually fade away.
I will be very surprised if we don't hit that tipping point in my lifetime. Say the next 30 years.
> I believe the folks worrying about IPv6 only are just looking ahead to a possible future.
I'm certain that that is not what the folks who scream very loudly about how IPv6 has been and continues to be a colossal failure because it's not the only version of IP on the Internet are doing.
> I do think it is reasonable to expect there will become a time when IPv6 is pervasive enough, that new deployments will target users with IPv6 rather than IPv4.
Sure. That's the future I find most plausible: For "residential" connections, provide IPv6 GUAs and IPv4 via CGN... [0] for "commercial" connections, provide IPV6 GUAs and give the customer the option of one or more IPv4 GUAs.
> I will be very surprised if we don't hit that tipping point in my lifetime. Say the next 30 years.
I do hope we get to that point within the next five years, if not ten! But notice that my claim is that IPv4 will still be crossing the Internet after everyone reading HN today is dead. [1]
[0] I'm calling the various mechanisms that only provide an IPv6 address to an end user and do fancy gyrations to provide IPv4 access "CGN", even if might not strictly be CGN.
[1] ...as long as the the responsible, level-headed type of folks that run it now aren't replaced with the "making backwards-incompatible changes to everything every six months is A-OK!" type of folks.