The Mini is the low end Mac product. If low end products get soldered RAM then they will get BGA CPUs that only take soldered RAM.
Sorry, but bga cpu don't imply only take soldered ram, actually almost all Mac line with the notorious exception of the iMac 27 and the Mac Pro all use bga soldered cpus.
The Mac Pro decided SSDs were "good enough" for all targeted users. It lost the capability to handle 2.5" drives. If Mini takes on same concept of only 'SSDs for everyone' then the 2.5" form factor for internal rotating devices will probably get tossed.
Not necessarily, as the iMac the ssd maybe only one storage option on the menu.
A mac-Pro like cylinder for a mini could use the areas dedicated to the dGPU for 2.5/3.5" hdd slots leaving all the thermal core available for the cpu cooling.
If it is a really a 'Mac nano' design they are after, then I suspect won't see a 2nd TB socket. The mini would start mimicking the MBA which is only a single TB socket.
While everything it's possible I don't think a Mac Nano will succeed the mini coz the Nano format requires external PSU, noisy fans (especially with iris pro, just peek at gigabyte brix Pro users for comments), plus restrictions to expansion ports.
A fanless , shrunk down , Core M based Mac Mini would re-purpose the name to a substantively new product like the Mac Pro was.
Why? , still mini.
I own a Mac Pro 6,1 and I use it for what is supposed must be used: workstation, only difference is when I see the nMacPro and the old Mac Pro is space saving and Quieter device, same purposed devices, just some evolution.
If not a 'Mac nano' design and Mini tracks the iMac (or rMBP) components then it probably won't be fanless . Dropping a fan completely isn't very efficient (in thermal transfer) or effective ( in size/weight ). Sure folks have done that in some products, but Apple doesn't necessarily adopt every dood-dad design trend of the general PC market.
FYI I build pc for professional flight simulation, of course I use pc hardware, I'm very familiar with fanless cpu coolers, and only thing I must with confidence is that you're absolutely wrong on passive cooling.
Actually am 120W passive cpu cooler it's something like 2x2x3" in size, with 25deg Celsius room temperature, cpu on heavy load don't rises over 80deg Celsius (sorry I'm not familiar with old Fahrenheit scale).
So a mac mini with 65w TDP cpu (as i7 with iris pro) could be cooled passively with an thermal core like design cooler much smaller than currently Mac Pro thermal core (active cooling) I speculate could be about 2/3 the size of a Mac Pro. Leaving room for 2 2.5 hdd where the dGPU are on the nMP, of course one of those 2 5 hdd could be replaced by an pcie ssd exactly as on the nMP.
Of course This is what I will do if I'm Johnny Ive, give all us an more powerful and absolutely quiet Mac Mini -pro.
Being realistic, I'm not surprised if the only change on the form factor is the removal of the firewire port replacing it with an 2nd Thunderbolt port. And internals upgraded to offer upto i7 + iris pro.
What would surprise me it's time see an dGPU on the next mini, thus will be an groundbreaking offering killing some iMac.