Wired says they've recieved a tip (from Captain Obvious?) that the Mac Mini is going to get a refresh. They predict (try to stay awake for this one):
Similar to the MacBooks, the Mac Mini will sport a silver enclosure composed of a block of aluminum.
Some internal parts will be PVC-free, and combined with its size and low power requirements, Apple will tout this as the "greenest Mac ever."
For video output, the Mac Mini will use the DRM-crippled DisplayPort for connectivity, which Apple is offering to manufacturers for a no-fee license.
It'll have a CD-DVD slot loader (i.e. Super Drive). There will be no Blu-ray player, because Steve Jobs believes the format is a "bag of hurt."