Ace2

Like Ace(1), Ace2's main purpose is (as stated to WoWace.com) to improve modularity, improve performance, and simplify the addon and library creation process.

Ace2 will replace Ace when it achieves gold status. Although Ace2 is currently under development, many popular addons are already using it's libraries.

Ace2 is Currently at END OF LIFE status, and is beeing superseded by Ace3.