According to this post on the WoW forum, the latest PTR (Public Test Realm) patch contains configuration settings to enable IPv6.

This would be the first big game to support IPv6 as a connection protocol. With around 3.5 million players from Asia, the part of the world most likely to run out of IPv4 the fastest, this is well thought out move.

Network (Including the lag optimization deployed in 4.0.6 and disabled shortly after)

  • OPTIMIZE_NETWORK_SPEED = “Optimize Network for Speed”;
  • OPTION_TOOLTIP_OPTIMIZE_NETWORK_SPEED = “Enable this option to optimize network usage for speed in order to decrease lag. This will increase your bandwidth usage, and may cause problems in some environments. Disabling this option may help resolve certain disconnection issues.”;
  • OPTION_TOOLTIP_USEIPV6 = “Enables the use of IPv6, the technology behind the next-generation Internet. Requires IPv6 connectivity to the internet. Checking this box without IPv6 connectivity may prevent you from playing WoW.”;
  • USEIPV6 = “Enable IPv6 when available”;
  • Lets hope other game developers start supporting IPv6. Are you reading this Valve?