I posted a very similar thread yesterday ("Late 2012 Mac mini: keep or sell?"). I have a 2.3 GHz i7 model that I upgraded to 16 GB of RAM and a DIY 2.12 TB Fusion drive. The only thing I dislike about it is that the old graphics adapter doesn't support 4K monitors at 60 Hz, but it still does everything else I need to do just fine. However, I also have a 2015 13" MBP, so having the mini isn't essential, and I'm tempted by the current high resale prices for quad-core minis. I, too, think that they might be peaking. If Apple confirms that a new mini will be released, then prices for the late 2012 quad-core models likely will plummet, unless the new version turns out to be as big a disappointment to most people as the 2014 version. At some point, though, it will be hard for anyone to justify paying so much money for a computer that came out in 2012.
I think it's extremely unlikely that Apple will release a new Mac mini of the kind that most of us want to see: current technical specs, quad core, multiple ports, upgradable RAM and HDD/SSD (even it's not easily upgradable), all at a reasonable price. That isn't consistent with Apple's current design philosophy. I'm not holding out hope that Apple will release any new mini, but, if they do, it likely will be a non-upgradeable, Apple-TV-sized unit with a couple of USB-C ports. I wonder, though, from Apple's point of view, what the market for a new Mac mini would be. The original model was meant to be a "gateway" product for Windows users who were curious about Macs but didn't want to spend a lot of money to check one out. Apple no longer has a brand-recognition problem. For users with basic needs, Apple now pushes the iPad.
My dream Mac wouldn't be a new mini, though: it would be a mid-range tower, the modern-day equivalent of my 2000 G4 Power Mac, which cost $1,600, and for which I upgraded every upgradable component over the next eight years, after which I gave it to my dad, who got another two years out of it before it died. That was my favorite computer of all the computers I've ever owned. We'll probably never see its like from Apple again.
If the Mac mini line is indeed dead, I wonder if the late 2012 quad-core models, like the Cube, eventually will become collector's items. The mini is an example of great design. It might be worth hanging onto for that reason, unless one really needs the cash and has no use for their mini.