Apple needs a machine that is user upgradeable.
No, they don't. Have you even paid any attention to the computer industry as a whole for the past ten years? The game used to be modularity. Now it's all about integration, with modularity all but thrown out of the window.
In 2003, full-size ATX motherboards were still the norm. microATX was gaining steam, mini-ITX were mostly for embedded systems like POS terminals, and VIA's nano-ITX form factors were more obscure than mainstream.
Ten years later, even microATX is too big, as you can stuff a full 95W TDP IvB into a mini-ITX board for a lean and mean gaming machine. The likes of Arduinos and Raspberry Pi's took over the smaller-than-mini-ITX market. ATX? Unless you love expansion or a hardcore gamer, you need not apply - and those people would have gone towards E-ATX anyways.
HP and Dell portable workstations used to have 16:10 displays. They're both going 16:9 now, so Apple became one of the last few vendors nowadays that continue to sell 16:10 laptops... and Apple doesn't use workstation GPUs in their laptops.
In ten years, Apple killed off XServe and exited the server game; put more money towards the mobile space than they did for traditional desktop/laptop markets; killed off the iBook/MacBook lines, and killed off the 17" MBP.
Ten years ago it was completely unheard of that a company with NO laptop computer building experience would put out an ultra-portable gaming machine that doesn't weigh over eight pounds fully loaded. Now we have Razer going into the business and show the likes of MSI and Dell how it's done.
Whats a "Pro" machine when you can't upgrade it?
If you're going to upgrade the GPUs, why not go the whole nine yards and replace the entire system as well?
I think apple will keep some type of cMBP model as replacement for the white macbook.
When I saw the MBPR came out last year, I knew the days of the cMBP are numbered. Right now the cMBP remains the only Mac in Apple's product lineup that retains the ODD. The iMac went towards a slimmed-down pyramid, the new "trashcan" Mac Pros don't have room for one, both the Air and Retina's tossed 'em out, and even the Mac mini nixed it.
Give it a facelift. re-market it. Give it user upgradeable features. Make it quad-core. give it 2.5" hard drive or even 1.8". keep 204 pin upgradeable ram with more than 2 slots for up to 32GB ram.
All in a 14" cMBP? No way.
If this gives you a clue: SSDs do not need to retain the same physical 2.5" format as HDDs without sacrificing performance.
