No-one really wanted a smaller Mac Pro, and even people who kind of did didn't need Apple to make such a huge reduction as they did (even half the size would have been a significant reduction).
The Mac Pro is smaller largely because Apple moved to embedded GPUs to align with Thunderbolt. That brings the Mac Pro into alignment with where the rest of the Mac ecosystem is going. Decoupling the Mac Pro from the larger Mac ecosystem wasn't working and that wasn't likely going to change.
Throw in the jihad on removing ODDs ( 5.25 bays toast ) , focus to SSDs, and bit of lowering shipping/inventory costs.
Finally throw on top targeting it as a desktop as opposed to a floor standing design and it is what it is.
It is smaller because much of the design constraints changed, not smaller for primarily for smaller sake.
Same kind of deal with the iMacs; I didn't really notice anyone complaining about the bulk of an iMac, but Apple made it much thinner anyway. Miniaturisation does have a certain wow factor if it can be pulled off.
Those are similar in the reduction of the Mac Pro to a smaller size but not particularly already small/minimized and push to smaller still.
The iMac tossed ODDs. If don't need a flat edge for the ODD anymore then it goes. Rearrange the internals so they are not gratuitously spread out and just simply remove some of the now empty space.
The iMac isn't thinner, the edges are thinner. Precisely where the ODD was dropped and highly symmetrical around the perimeter.
there is little miniaturization there at all. It is the heavy bet on digital transmission (and Flash based sneaker net ) over sneaker net with optical drives that is the driving factor.
The Brix doesn't seem to suffer either of these issues; it still manages to be a great little performer in a tiny profile.
Performer relative too ?
The iMac was handicapped a bit when it had laptop graphics and CPU. Since, enabling a desktop CPU the iMac has been on a substantial growth path. The Mini hasn't.
Strategically it would probably make more sense to shift the Mini from tracking laptops to tracking the iMac ( at least the 21.5" models ).
Instead of retreating backwards in cohort performance, standing ground and trying to put more value into the fixed price point that Apple is at.
Brix Pro is more expensive than an Mac Mini and it doesn't even have an OS that needs to be paid for.
Anantech's completed system is far over the Mac Mini price point ( $900+ )
http://www.anandtech.com/show/7648/gigabyte-brix-pro
Haven't even gotten to Apple's 30% mark up.
but with better and better power efficiency in all components, it's definitely possible to slim down.
Better power opens the door for additional functionality if leverage the trade-off. Iris / Iris Pro power efficiency may go up but the pricing isn't going to crater as fast. Shrinking the Mini "too small" likely means there are certain CPU/GPU performance options not going be able to leverage. Products that plug into the wall just are not as driven by power as primarily battery operated systems are. Apple could chase the battery systems with the mini but the real market competitors don't have that limitation.
While I don't personally want them to, there is definitely room to do so; a Mac Mini doesn't strictly need an Ethernet port when you can use a Thunderbolt adapter, especially since it has good built in WiFi. FireWire is bound to go, and there isn't really much reason for the Mac Mini to have an SD Card slot on the back (it's not very easy to use in that position). So if they need to trim I/O there's plenty of options that don't really cause the Mac Mini to lose anything.
Following the MBA for cues is highly unlikely to make for a system competitive in the desktop market. Apple could move the Mini out of the desktop market
None of the other Mac desktops are dumping Ethernet. Not sure what benefits it has for Mini given those as sticking with it. The more cluttered Wifi RF space gets the utility of having wired Ethernet goes up.
Firewire sure... it is gone from the other desktops. But those also have two TB ports. Mini would likely trade rather than reduce.
SD card sneaker net is bigger world wide that most folks imagine. It also don't buy any space either unless toss the audio input and output out the window also. ( it is a shared space vertically).