In order to maintain its extensive deployment matrix, Liferay up to 6.1 has been locked to Java 5 APIs.
However, Java 5 started its EOL cycle on April 8th, 2007 and completely it on October 8th of 2009.
Furthermore the last app server that still required Java 5 has finally been EOL'd itself at the end of 2011.
This means that Liferay 6.2 is now free to adopt Java 6.
It's true that Java 6 itself is almost EOL (extended through Feburary 2013), but due to the transition period lasting an estimated 2 years for clients with support contracts, it means that many enterprise applications will remain Java 6 dependent untill the very end of the transition period which also demands that Liferay remain complient if it wants to retain those applications as part of the extensive deployment matrix it currently enjoys.
This of course in no way prevents 3rd parties from developing plugins/extensions against Java 7 or later as long as they accept the limitation this will have on deployment.
It was also suggested that the community should be informed (as the documents have not yet been updated) that building Liferay 6.2+ requires Ant 1.8 or greater. This is a minor point but can cause frustration if one is not aware.