And will be out by the end of the year! So perhaps a soft launch in December 2023, with BTO availability by February 2024!
It's Apple's SOP to re-use the chassis of the previous machine during an architecture transition, to maximise the 'nothing to see here, move along folks' effect, rather than freaking people out changing everything at once.
The lack of RAM upgrades is not a surprise, though the idea of a large, fast local pool + DDR5 slots for capacity did seem intriguing.
Gurman doesn't specify whether those upgrades can be done post-purchase, though being able to fit PCIe-based SSDs and network cards is pretty unremarkable for a tower.
The ability to upgrade the GPU is what a lot of the discussion has hinged on, given the lack of AS API support for PCIe / TB GPUs, or AMD drivers for them. As
@deconstruct60 suggested earlier (bottom of this post:
#546), strictly compute-orientated GPU modules would be a lot more straightforward to integrate than an external display GPU, though.