That's already the case. IPv6 is often faster because most ISPs these days use cgnat for IPv4.
This becomes noticeable when pipelines on IPv6 connected servers suddenly have random request/post failures to public services. Then either the whole service is temporarily having issues or there are a few bad IPv6 endpoints while all the IPv4 endpoints are fine.
Seemingly this failure mode can go unnoticed for days while the same won't be true for IPv4 due IPv4-only still being the norm for corporate networks. And no, current form of happy eyeballs v2 won't account for this.
Besides bad endpoints it could also be a problem with bgp route advertisements where the IPv6 prefix takes a weird path and ends up being blocked by a CDN at the other side of the ocean. This happens more than you'd think. Obtaining pypi packages was quite a challenge last year for us for a couple of weeks due to this.
Not really a fault of IPv6 technology wise, and in general can be solved client side through retry functionality, but in practice it still can lead to a worse outcome due to lackluster IPv6 adoption.
I used to think ISPs, organisations, admins and users were just being lazy for not implementing IPv6 or turning it off as the first thing to do when network problems happen, but when this far in the rollout such basic things still lead to difficult troubleshooting sessions then perhaps time has come to say something has gone terribly wrong.
It saddens me to say that I totally understand that businesses do not want to pay the price for implementing IPv6 unless absolutely necessary, because until the majority of traffic is IPv6 or even IPv6-only it does not make a lot of sense.
The flipping point is nearer than ever, though I fear it will in the short term lead to even worse stability for both protocols until IPv6 truly becomes the norm, whenever that may be.
If you've ever visited a website from your smartphone (over 4G/5G), your first hop has in all likelihood been over IPv6. If you have visited a website from your phone that only had an A record then you probably went through a CG-NAT box, which added latency.
If you streamed a Youtube video to your phone, or checked Gmail, or Instagram or Facebook, then it was over IPv6.
People (including probably you) use IPv6 everyday, multiple times, without knowing it.
Also there are cases where the ISP didn't bother even optimizing their routing in v6. I understand that some ISPs in Asia (and especially in Japan, where it shows up on ordinary customers in terms like MAP-E and VNEs) have separate backplanes for v4 and v6 (some are legacy reasons, some are business reasons). Guess which one is being devoted more in practice (hint: not the one being devoted more by IETF).
Edit: I thought this was just in Asia, but apparently this is also the case in an ISP in UK (https://news.ycombinator.com/item?id=48618403)
Do you have examples for this? I've never experienced this, and I've been using IPv6 for years.
Also, how can you be sure that the same request to IPv4 would have been fine? Did you actually see consistent failures on v6 and consistent success on v4? Otherwise, if a service has a reasonably low error rate, success on retry is the expected outcome, regardless of the path the retry takes.
This happened with pypi (IPv6 BGP routing problem caused by a bad route from one of our peers combined with their fastly CDN not reply to us on IPv6 from the other side of the ocean for some weird reason), but also with yum and apt mirrors (seemingly random problems with the IPv6 service or firewall of the remote endpoint), and various other web resources accessed from pipelines.
The solution always was to temporarily block the bad IPv6 endpoint(s) or temporarily completely disabling IPv6 on the server itself or on the squid proxy server for workloads without direct connectivity.
Obviously it also can be the other way around, but in practice it appears to happen less often with IPv4, and if it does things get addressed quickly instead of taking hours or days or weeks.
Users doing speed tests in CGNAT may be seeing numbers that aren't exactly real for a (still) mostly IPv4 Internet.
Infact the only isp I have seen do it is starlink and I have contacts with ISPs in 60 different counties.
More on this: https://vincent.bernat.ch/en/blog/2024-why-ipv6
Unless you want to host multiple minecraft servers on the same port on different servers at home?
Indeed hosting anything at home is such a rare workflow that someone wanting it can choose an isp which gives them the facilities they need.
Unless you don’t live in a competitive market based economy and just have the single government mandated isp aimed at the lowest common denominator, in which case you’ve got far worse problems.
If there's one thing market competition does well, is remove any kind of meaningful variety - because supporting a niche offering costs money, and is not worth it unless it nets positive, otherwise it's just a drag that makes you fall behind your competition.
The internet would be much less centralized if IPv6 happened when it was supposed to.