One thing they can do, and I would live to see some popular destination
site do this, is to say something like:
"we have this really cool new thing we are rolling out but, sorry, it is
available only via IPv6" or "we will continue supporting all of today's
features on v4 but all new features will be rolled out on v6 only".
I doubt any top web sites or popular services will do this, because
there is no commercial advantage to it. It is great to see Google,
Yahoo, and other companies taking a big step by deciding to serve up
AAAA by default for one day. It also should indicate to everyone how
far we are from the goal line, not because Google or Yahoo aren't
doing their homework, but because their end-users' ISPs aren't. If
these companies are only willing to do AAAA by default for one day on
a trial basis, and that with months of notice and perhaps preparation,
they clearly should not be willing to make some cool new
revenue-generating feature exclusive to IPv6 end-users.
If I recall Comcast and Time Warner are participating in IPv6 day. This should create enough eyeballs to show on web analytics graph and provide the shift that makes nat444 irrelevant.
I am afraid you may be a little disappointed. The number of users
with IPv6-capable CPE, to say nothing of home LANs, may still be quite
limited by that time. It's still progress, but I don't think anything
except IPv4 depletion will increase IPv6 adoption.
For a network operator I'm looking at the ipv6 ipv4 ASN ratio. Once it passes 10% we will have a snow ball effect in the core.
Unfortunately, many ASNs who originate IPv6 address space have few or
no functioning services on IPv6. A simple "ASN ratio" is not a very
useful metric. You also do not have visibility into how much
infrastructure is based on tunnels, whether or not v6 even reaches
customer access ports or even is enabled backbone-wide, etc. I agree
it is encouraging to see new ASNs originating IPv6 routes every day,
but again, this is more an indicator of "we got a /32 from the RIR and
configured it on our router" than "we are using v6 in a production
capacity (or are prepared to flip the switch.)"
I really do think that advertising may be the thing that eventually
forces some end-user ISPs to get in gear. If end-users went to
www.google.com on "IPv6 day" (and perhaps after) and got a message
saying "your ISP is great" or "here are some ISPs you might want to
consider, because yours can no longer reach some Internet
destinations," I suspect that would give ISPs a very serious reason to
spend the necessary resources to get v6 done.