Apple may have let slip a long-awaited Mac mini update in the depths of its support site. In a Boot Camp article listing Windows compatibility and system requirements, a new line item popped up in a table of Mac mini models.
With newest models at the top of the table, you can see the Mac mini section includes a "Mid 2014" line item, which happens to be the part of 2014 we're in now. There has been no word from Apple on a new version of the Mac mini, although we have had other updates, such as the recent iMac update which is classified as Mid 2014.
Over at MacRumors, the Buyer's Guide shows the last time various hardware was updated, and it shows the last bump to the Mac mini was October 2012, 644 days ago (as of today) and the average is 373 days.