Yeah, it exists in hardware implementations too, but most devices that have IP stacks (of either IP version) do it in software because they're general-purpose c

Yeah, it exists in hardware implementations too, but most devices that have IP stacks (of either IP version) do it in software because they're general-purpose computing devices. And it's the general-purpose computing devices that are lagging in IPv6 support, not the networking-centric hardware implementations. It's been quite a while since business-quality networking devices shipped without IPv6 support. For those home / small-business routers which still lack support, that is probably going to be a software implementation either way, and at the very least the software nature of any IPv6 implementation added through a "firmware" update (really just an OS update) won't be a performance bottleneck for those devices. In some of those cases a firmware update has even been released by the manufacturer, just not applied. In many more, IPv6 is supported by the networking device and the software/firmware but simply disabled, or not supported by one or both of the ISP and the end-user device.