I agree, but more and more customers are strictly limiting egress for security reasons which reduces the argument somewhat. I think it’s more likely that not overpaying for NAT Gateways will be a more effective source of pressure for AWS customers.

> Running single stack hosts is absolutely a reasonable goal.

Sure. I expect that it's not one that we will see most Internet-facing machines achieve in our lifetimes.

> If i have choice between running ipv6 and nat6to4, and ipv4, ipv6, and nat4, surely the former is both a simpler setup...

No. You already have an IPv4 stack in your OS, and I guaran-damn-tee you that your NAT64 setup is far more complicated than a NAT44 setup. [0]

> ...and a further step towards a real full v6 internet?

Sure. But there's no inherent value in dropping IPv4. The only thing wrong with IPv4 that's not also wrong with IPv6 is that it doesn't have enough address space. Moving more and more globally-reachable servers and hosts to IPv6 reduces the number of IPv4 addresses required, which solves the "not enough addresses" problem of IPv4.

[0] AFAIK, if you use NAT64, you either let both direct-IP connections [1] and inbound IPv4 port forwarding not work, OR you must use additional (substantially complex) software to make that work. So, either you break some software that happens to use IPv4, or you massively increase your system software complexity. Seems bad either way.

[1] That is, connections to IPv4 hosts without a pre-connection DNS lookup.