Fun numbers:

Academic price on a Mac Mini with 3.2GHz six-core, 32GB RAM, 1TB SSD: $2309.
Early 2014 academic price on a six-core MacPro with similar specs: $4319 (or $4642 in inflation-adjusted dollars).

So... prices have definitely improved, but performance? Probably close to indistinguishable. But is it modular? Presumably, now that Apple has brought the Mini back from the dead, the 3rd-party ecosystem will start stamping out lots of gadgets in the same form factor so everything stacks nicely. That presumably includes eGPUs, disk enclosures, and so forth.

I've read a few articles lately about how Apple doesn't want to play nice with NVidia. We can only hope that this nonsense gets straightened out as part of the migration to eGPUs.