This embargo affects not only Redbox and Netflix, but Blockbuster stores as well.
Warner Home Video has never been a fan of the whole Redbox and Netflix thing. They say that the low priced rentals are hurting sales and are doing what they can to cut down on the effects. It's not surprising then that Warner is looking to expand their existing 28 day embargo to 56.
What does seem a bit out of character is that Warner isn't just targeting Netflix and Redbox this time. Not only is the company expanding the embargo on low priced kiosks and subscription services, they're applying that eight week embargo to Blockbuster stores as well.
It hasn't been officially announced at this point, but it seems fairly likely. Adding the delay would be a move not only to increase DVD and Blu-ray sales, but to push the digital copy storage locker UltraViolet which is getting a big push this year.
Source: Home Media Magazine