OK, on what basis do you think the more likely outcome is that a new Mac Mini (which is almost certainly coming) will have the same ports as now.
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....... Which was an update on the 2012 Mac Mini.... Firewire 800 was dropped and the single Thunderbolt port was upgraded to two Thunderbolt 2 ports for 2014.
I should have said "look to iMac as a guide", rather than being the same....
For the Mac Mini there will be an upgrade to Thunderbolt 3 / USB-C, in keeping with updates across the Mac range.
In keeping with the iMac, USB 3 will be retained, as will Ethernet and likely the SD card slot.
The 3.5 mm audio out will remain, but the audio in port may be dropped, as has been the case across the Mac range. Audio in can be handled using a USB-C hub.
HDMI will be retained as the current standard for connecting to a monitor or TV, as befits a consumer oriented machine. Yeah, yeah, the iMac doesn't have HDMI, but Thunderbolt 3 / USB-C can handle a dual display set-up.