It's really not though. ISPs are a problem, but every hosting provider I've used has offered IPv6. It's really trivial to setup IPv6 name DNS, and host a website on both IPv4 and IPv6. I just do it by default now.
Once it becomes the default to deploy to both, if IPv4 died then the IPv6 side would just keep working.
For DNS, you can make a single glue record contain an IPv4 and IPv6 address.
DNS just needs A and AAAA records for the Name servers. NS records still point to the hostname as normal.
For Web servers, the web server just needs to bind to the IPv6 address(es). Then in DNS just have an A and AAAA record for each website hostname. The server name directives will cover both.
There really isn't much to it right now. The technology is mature now. It used to be a pain, but now it isn't.