The Mac mini turns 4 this week. Some "rumorists" are forecasting the update will be announced on Oct 30 at an event in New York.
MacRumors.com (https://www.macrumors.com/2018/10/17/mac-mini-four-years-since-last-update), Oct 18, 2018
My "new" one is still under AppleCare, so I won't be in the market. [rolleyes2]