Over the last few days shipping times for Mac mini desktop computers on the Apple U.S. and Canadian online stores have slipped from the usual "Within 24 hours" to "1-3 business days" suggesting a shortage of Mac minis and a potential refresh in the near future.
TUAW also notes that the iMac which has been rumoured to be imminent for a refresh is far below normal stock levels at one Apple retail store.
Rumours over the last few weeks have pointed towards a refresh of the iMac and MacBook, the Mac mini was conspicuously missing from these reports.