And yet all the _software_ developers who matter did just this. I was using IPv6 _software_ ten years ago, maybe closer to fifteen now. Our biggest worry in _software_ is Microsoft Windows 95, long obsolete and unsupported, but widely used for the same reason people are still watching TVs with dial tuners (yes, really, they are even in countries with DVB - backward compatibility is a bitch)
So software is great, it's enough to have IPv6 in your house, share it with a few friends in a tiny startup's office, or even across a few hundred hosts if you can afford a beefy FreeBSD box as a router. All these things were being done last _century_ in preparation for the transition we are now undertaking.
But that only gets you so far. Eventually (today probably somewhere about gigabit speed) it is only cost effective to switch IP with custom hardware designed for that specific purpose. Eventually the cost of wider addresses doesn't vanish, but instead dominates. And there the story changes.