I actually shared similar sentiment, like a day or two right after the roundtable, and was pondering about the possibility of some surrealist modular space ship hologram tier design. But reality quickly came upon, and it became obvious that the machine needs to be a solid performer much more than a fortune teller. You have to put into perspective of Apple's position that they put themselves in, by stagnating the workstation line up for 5 years+, pretty much sat and watch the VR/AR/AI/ML waves passing by while they struggle to balance TDP inside that triangle core. When they said "designed into a thermo corner if you will", they didn't just throw out a catchy line, it was literally what happened and they are embarrassed to admit it, but they had to. The biggest problem with the trashcan MP wasn't in the details, but the idea behind: they foolishly thought industry trends wouldn't change in directions where a self-limiting form factor wouldn't become an issue. After all that has happened, I will be shocked if they don't stick to the basics and just make a vanilla box, just for now.
This is not to say a truly modular approach won't be a thing down the line though. In a way, by mandating Thunderbolt across all Macs is already creating modular setups on user's hand, it is just that Apple itself doesn't offer all the parts (if any). I am unsure if Apple are even interested in backpedalling in this case, they already pulled out of AirPort for one, which you can consider to be a wireless module. They were going to pull out of display but they they are going to be back. Some would really like to use iPad Pros as macOS stylus and/or external display, but then that's already semi-possible with 3rd party apps. Same with using iPhones as touch interface. And then we now have AirPods and HomePods which are essentially audio I/O modules. Notice that a lot of these are already pretty useable over wireless, so what's left to be solved are high bandwidth low latency components, the core system if you will, which obviously should be wired. For these parts, Apple seems to think that putting together a disposable machine with much shorter expected life span than we are used to is the way to go, instead of offering space and slots unused by most users. As it stands right now there is no sign that Apple will drift away from this approach, but we will see.