updated 03:22 pm EDT, Mon July 29, 2013
Product refresh on July 30 still possible
Following reports last week of the Mac mini's availability tightening to one-week shipping, all stocked models on the Apple online store show configurations available shipping normally, "within 24 hours." At no point during the time that shipping availability was 5-7 days was the machine generally not available at Apple retail for pickup.
While it remains a possibility of a Tuesday July 30 product refresh given the recent release of Intel's Haswell fourth-generation core processor line, it appears now that the limited availability was a transient situation. Apple generally holds less stock than competitors, with the target being one month or less of computers, and four to six weeks of mobile devices like iPhones and iPads, so brief periods of longer-than-normal shipping do happen on occasion.
The last Mac Mini update was in October 2012, at about the same time that the fourth generation iPad and iPhone 5 were released. The last two refreshes of the product before the current Mac mini generation took over 400 days between generations.