Don't think their numbers are right.
I manage 3 different sites with AAAA and A records.
site 1: tech site: 12% of the traffic is via IPv6
site 2: mixed/funny site: 7% is IPv6
site 3: company site: 9% is IPv6
I asked around a few friends and all of them with IPv6-enabled sites have around 5-15% of their traffic via IPv6.
Even Google sees 14%:
https://www.google.com/intl/en/ipv6/statistics.html
Can't believe this 50% number.