We've confirmed with trusted sources that the black Xbox 360 is indeed coming (the image above is of the original 360 dev kit, FYI), and will be dubbed the Xbox 360 Elite. Here's what you need to know about it:
The Elite will be limited quantities only; that may be as much or as little as a couple hundred thousand.
The case, controller, and Live headset will all be black. It will have all new packaging.
Elite will cost $479, and will be a 3rd SKU; it will be sold alongside Premium and Core packs.
Eventually Elite hardware (in white plastics) will take the role of the Xbox Premium. That is to say, after the Elite is launched and sold out, future Xbox Premiums will have 120GB / HDMI.
We do not yet know exactly when 120GB / HDMI will become the standard for Premium, but it is loosely estimated to be late summer or fall.
Elite models run cooler than normal 360s, but they are not yet confirmed to have 65nm chips.
Prices may remain the same with the 120GB / HDMI hardware upgrade in the Premium Xbox, but we may still see a price cut on the line when 65nm chips start shipping.
The HD DVD drive will not be internal or bundled -- Microsoft never did or nor does not currently have plans to put an HD DVD drive in the 360.
There are no current plans to integrate WiFi into the Elite or future Premiums (although that can always change).