A new Xbox 360 update should be up very soon as confirmed by Major Nelson.
Major Nelson tweeted the following about the Xbox 360 update:
An #Xbox360 update hits as early as tomorrow, mostly back end stuff. Start an #XboxVideo rental on Xbox 360 & pick it up on another platform. That’s one of the only new features.
By the time you read this, the update should be available for you to download and install. It’s sounds like a small update so you won’t have to wait long.
I just got the update right now