All these people talking about a 6 core Mac Mini and I'm over here tickled pink by the thought of it just going back up to 4...
Here's the deal...Apple has several different CPUs available from which to choose. If they keep the existing mini chassis, they could easily use the 15w U-Series (7th or 8th Gen), the 28w U-Series (again, 7th or 8th Gen), the 45w H-Series (and again, 7th or 8th Gen) OR really surprise us with at least one model sporting the 65w G-Series (Core i5-8305G or Core i7-8705/6G) as a BTO item. I think after 4 years of complete stagnation, any of these CPU choices would be welcome by those of us either have a mini and want to upgrade, those who are considering macOS or those who use the mini in a number of different vertical markets.
The unknowns are how much RAM it would ship with as base (should be 8GB), will it support up to 32GB of RAM, how many TB3 ports it will have (two is easy and cheapest) and will it come with the ports that most users would expect as they have them on their current minis (USB 3.0 Type-A, HDMI, Gigabit Ethernet, SDXC, Audio In and Headphone)?
Although the motherboard would be completely new, there's no reason why they couldn't simply use the existing chassis, improve any cooling needs to support a G-Series CPU and get it out the door. After the debacle of the 2014 model, it would be nice to see Apple do what it rarely does anymore, which is surprise us with what we asked (have been asking) for since the 2014 model was released. The 2012 model seems like such a fluke now and it shouldn't. It is quite frustrating to see Apple so consumed with trying to make us believe that the iPad is what we want and need, when that's not at all going to work. Maybe they are listening, but I am not holding my breath.