You are at Cuppertino where Cap. Cook decide and dont care about how do you behave past year, not the North Pole Where Santa's cares you behave well to give you what you want.
Being realistic, I understand budget minded people, I used to think the same way, I purchased my MP only with D700 GPU, ad 4core cpu and 12gb ram, then I upgraded it to 8 cores and 128gb ram, It's Ok, and believe Apple wont prevent you to do that again (me too), with one exeption: GPUs, for two reasons: high powered PCIe devices are more prone to electric short when in a DIY upgrade scenario, not the same as the ram, even the CPU statistically its much less prone to cause MB shorts in DIY upgrades, also add to that a technical reason Apple needs to re-reoute the DisplayPort Output to the Thunderbolt 3 controller, current ISA gpu provides 4 DP 1.4 ports, good to feed 4 TB3 controllers (8 tb3 ports), as its projected the next Intel Skylake-W PCH to allow 44-48 CPU PCIe3 lines good for 2 GPUs and 3-4 NVMe or 3-4 TB3 Controllers, also there are 20 extra PCIe3 lines from the PCH to add extra TB2 controllers (maybe 4), 10GbE, WiFi/WiG etc to the Mix, dont expect to see any Sata drive support, neither DVD/BD-RW driver support, also given Intel has commented Xeon Skylake-W will be offered as single socket for workstations and Skylake-P for servers/compute applications on 2/4/6/8 Socket configurations, also accoutn how many cores it has (32 as latest leak) even the same socket/chipset allows Xeon Phi 2xx upto 72 cores, I dont believe Apple will mess with dual socket support which will translate on cheapo upgrades and very rare dual socket systems being ordered, its not the case as the RAM (wich Xeon Skylake-W allows 6 channels, easy for 96GB on cheap 16GB modules, or 192GB on 32GB quite expensive modules), also Apple may give the same on the Storage, allow M.2 NVMe std instead proprietary, since it has economical sense to save few R&D $ on something doesnt worth to protect from commoditize, but they also may re-cycle NVMe from the iMac and keep storage propertary, but at least unlikely it will be soldered.
About how the next Macintosh Pro will look (phil 'my ass' schiller also give us the hint: it will be proudly named Macintosh again, read the transcripts), its less meaningful, but it dont need to be a Under-Desk Monster, while it certainly wont be as minimalistic as the TrashCan, but sure will look good at the the desk along the Keyboard and other peripherals.