The "Anniversary Edition" slipcovers are for the "Looney Tunes" franchise's 90th anniversary next year. Among the other titles being given this treatment are The Essential Bugs Bunny, 4 Kid Favorites: Looney Tunes Movies (and all four individual movies included in it), and Best of Warner Bros.: 50 Looney Tunes.
On a slightly unrelated note, the first four volumes of the Golden Collection are being re-released at around the same time in the same plain keepcases they came in when sold together (from 2011 on). One must wonder if retailers like Amazon are already selling them like that, because when I received the sixth volume for my birthday eight months ago, it came in a keepcase instead of a slipbox and Digipak...