believe me i agree with you. i think an affordable tower-style mac would be awesome, and there would be a ton of people who would agree. i would be extremely interested in it.It's not here yet.
So you're asking who a computer that hasn't yet been released, specced or priced is aimed at and then dismiss the answers you receive.
We can only answer who we feel it should be aimed at, and the easiest, shortest answer to that is it should be aimed at those who are still using classic Mac Pros as by definition they are the ones who Apple haven't yet met the needs of with any of their existing products.
There are a significant amount of users (like me) who require the flexibility offered by a tower based Mac system.
I have traditionally used Mac Towers all along and in my time I've owned a 7200, 9600, G3, G4 (every incarnation), Dual G5, Quad G5, Mac Pro 1.1, Mac Pro 3.1, Mac Pro 4.1, so if Apple don't think I'm their target audience they are deluded!
I'm not a Pro, but I am most definitely a Power User and have been for two decades. If the next Mac Pro is priced so highly that it's only affordable to professionals or the extremely wealthy it will fail - however powerful or flexible it is.
It's not just professionals who need the flexibility offered by a tower.
The next Mac Pro should be scalable and should have an entry level price point under $2500 which would meet the needs of power users like myself, but could also be specced into the $10,000+ mega systems that may be required for those at the cutting edge who require such power.
it won't 'cannibalise' iMac sales or Mac Mini's because those still using cMac Pro's aren't buying those anyway.
I think those of us still using a cMac Pro require the flexibility of an expandable internal system with replaceable parts and that brief is not met by the 2013 trashcan Mac Pro, iMac or the new Mac Mini.
Hopefully the new Mac Pro will fill that gap - just like it did before, but if Apple still choose another 'solution' it will likely fail again and they'd have no one to blame but themselves.
also, you're right that we have no solid evidence on the cost/specs - it's all just speculation based on previous versions and how they aligned to their other products in terms of price and specs. so i'm just assuming that it's going to have an astronomical price tag along with proprietary upgrades (or extremely limited), and form is going to take precedence over function.