There's a lot of speculation about the Apple TV display. I think there will eventually be one but I also think there are greater opportunities for Apple. A computer display with built-in Airplay would help to transform iOS into a full fledged computing platform. But the display must be paired with a changes in iOS mirroring.
I agree with Viticci's assessment of the iOS-ification1 of OS X. But there is one feature missing from iOS that will prevent it from ever being effective with an external display: a cursor. I know this seems blasphemous but if you have ever tried to us an iPad with mirroring, you know that you must still look at the iPad to get anything done.
To use the iPad as a desktop replacement, mirroring is not enough. I need a cursor displayed where my finger touches the iPad (or iPhone) so that I have context on the external display. Every time I see iOS app demo videos they are accompanied by cursor representations for the touch interactions, and I think "that would be a great feature on the AppleTV."2
This current model of direct screen interaction is one reason many people have a hard time accepting the iPad as a true PC alternative. Every PC I own allows me to connect an external monitor. The iPad is almost there. One more layer of indirection is required to make it a viable replacement for me. I don't want to look down, I want to look ahead.