D&D Next is the prerelease term for Dungeons and Dragons 5th Edition, written by Wizards of the Coast, to be published in Fall of 2014. D&D Next is a heroic fantasy RPG inspired by the mechanics and settings of all previous D&D editions.
The final playtest packet was released in September 2013 and is no longer available. Every iteration of the playtest tweaked the core rules and the classes to try out different mechanics. The final version of the product will ship with multiple rules modules to customize the play of the game to meet your group/table's preferred style.