What we do know is that Apple has been internally testing Time Capsules to cache Software Updates for both Mac and iOS devices. The way weve heard it works is that the new Time Capsule learns which devices connect to it via Wifi. It then goes out to Apples servers and downloads Software Updates for those products.
This would let local machines pull updates from the Time Capsule and likely preserve bandwidth if you have multiple machines needing the same update.
The site also notes that Apple could expand on this capability for its new cloud service; perhaps using the Time Capsule to cache part of your cloud music library.
Both MacRumors and TUAW noted supply constraints yesterday for the AirPort Express, AirPort Extreme, and Time Capsule.