Sadly, this is the one piece of the operation about which there doesn't seem to be a flood of rumors, let-alone informed ones.

Being Apple, could they possible have a joint announcement planned for both the facility and for a total makeover of XServe line (emphasizing GreenPower, price-wise farm-suitable servers). Would it not be embarrassing for Apple to stock the place with a non-Apple product? At the same time, would it not be absurd to risk the success of a data center this size on an (relatively) inefficient, second-rate hardware config?

Either way, it should be an opportunity for a huge Apple PR event.