Pragmatical you have that backwards. Thunderbolt is aimed at max performance around the limitations of form factor being used (i.e., without PCI-e slots). It isn't being aimed at the most price sensitive parts of the market. It was never designed to be the low-price, volume leader solution. The move to copper was a compromise to get this jumpstarted. Originally this was "light peak' and things were all optical fiber. That isn't consumer oriented.
Thunderbolt is primarily aimed at boxes that don't have a couple of PCI-e slots though. It really isn't a consumer vs. professional thing.
In regard to budget portables, it wasn't aimed at that (didn't mean to give that impression). But compared to workstations, I do see it this way, though it is a significant boost for the top-tier laptop segment as it's currently implemented (more usable implementation than something similar to PCMCIA for higher bandwidth devices).
Now if they do get the optical portion sorted, and particularly if they also add features such as networking capability, that will change matters drastically in the workstation and server markets (what I suspect the long term plan was from it's inception, but ran into technical and cost issues <optical transceivers in particular>). So they decided to use copper as it would not only get it into the market to assist in recognition and at least start adoption, but to also reclaim at least some of the R&D already spent on it's development.
If Apple had moved the iMac closer to the HP Z-1, then perhaps. The fact that they went in 100% the opposite direction, I think it is likely they want to give Mac Pro another shot.
I've a strong suspicion that Apple could see the inclusion of TB in the iMac as a means of competing without having to give users access to the internals.
Particularly since they don't really offer a lot of GPU choices even for the MacPro (won't see a need to allow users the ability to upgrade the GPU). Combine this with a 3yr support cycle, it lends me to believe that Apple would rather limit user unreadability (forced obsolescence) as a means of selling new systems, as that's where they make their money (not really a software vendor comparatively speaking).
There is no way they are going to get workstation like performance out of that form factor for the never 3-4 years if that's the direction going. The Mac Pro needs to be re-jiggered though to pack in the performance it needs. Bigger power/thermal envelope for the PCI-e thermal zone. That doesn't necessarily mean bigger case but it doesn't mean anorexic diet either. Apple has the anorexic options they don't need yet another one.
I don't disagree, but I'm not sure this will actually happen at this point.
By skipping out on the latest SB5E Xeons, they wouldn't be able to cover what R&D would be spent on the next round of CPU's (same market position) by as many systems since they've skipped on the first half of the cycle for LGA2011 sockets.
So it seems to me, that they will either kill it, or replace it with something using a CPU from Intel's Mainstream line-up instead (even if it is a tower of some sort). Performance would diminish comparatively speaking to currently available MacPros, but combine the ability to sell to more enthusiast aligned buyers and lower production, they have the ability to keep the margins they've become accustomed to with a product with a higher growth rate as well. So far more attractive to them financially speaking.
It is stagnation and commoditization that would be the primary killer factor.
This is a major part of my point (may not have fully explained it).
I actually think this is currently the case when I look at the various pieces of information. The general trend for the workstation segment is shrinking, and if you combine this with a small market share, little if any growth, and the outsourcing of the hardware design and manufacturing, it really doesn't look good to me.
I don't see this much different than the race to the bottom that brought about the budget-box consumer systems, or other products (rebranded Funai products certainly come to mind for example...).
If the design is outsourced too, that's a bad sign. If Apple is just primarily designing the case then it is on thin ice. There are tons of more interesting and creative projects than just generating yet another box with slots.
The only part of the actual machine design that Apple has retained is the Industrial Design aspect, which has been stagnant for the MP for years. And of course they still do the software development.
But as per HW design, the MP has been outsourced since the move to Intel (Intel initially did the boards <'06 - '08 models>, but they shifted to Hon Hai Precision from the 2009 models to date). HHP gave Apple a discount on final assembly as a means of obtaining the more lucrative board contracts.