I am too. I think there will be some modularity - but it will be proprietary, and a huge arrogant mistake by Apple.
I, like many, are being forced to consider a PC build.
The new RTX 4090s are going to rip the M2s apart for my needs. I'm a professional creator (3D, film, etc) and quite a lot of the intensive tasks I do are moving to GPU processing, and apart from the VRAM headroom, the GPUs just can't compete with a pair or quad RTX cards (particle dynamics, Octane/Redshift, etc).
The hope I have is that Apple forget about saving electricity, and sticking mobile-focussed silicone in a work station and unleash a monster in the Mac Pro.
My day rate won't struggle to cover the extra power consumption. But my time will have an issue with slow GPUs.
Let's see - we only have to wait a month or so to see into the future. Mac Pro vs Threadripper Pro & RTX 4090s.