Question to Google

[bortzmeyer at nic.fr (Stephane Bortzmeyer)]

> 	Unfortunately, every time we've looked at the data, the
> 	conclusion has been that it would cause unwarranted user
> 	impact. IIRC the most recent blocker was a major US ISP whose
> 	clients would experience breakage if even just one NS record
> 	was dual-stacked.

There are many zones (including your isc.org) that have several name
servers dual-stacked, and they didn't notice a problem. Furthermore,
since the DNS is a tree, resolution of google.com requires a proper
resolution of the root and .com, both having IPv6 name servers.

So, this answer is at least insufficient.