We know that Apple uses x86 macOS Servers internally on commodity hardware (from previous discussion on HN[0]). Presumably, they'll need to keep some way of booting on machines missing the special Apple security hardware while staying secure, so Hackintoshes will always be able to find a way, since macOS will have to be able to boot on non-T2 systems for quite a while [1] (some machines they sell don't even have them yet, and presuming they keep up the 8-10 years of software support, there's nothing to worry about).
That thread mentions Apple using a combination of linux and macOS on commodity hardware for workloads that weren't suitable to their current hardware. If the Mac Pro satisfies those workloads now Apple is free to make the T2 chip mandatory.
Their own security makes a mandatory T2 chip inevitable imho - there were dubious allegations they were using compromised motherboards in servers last year, it wasn't true but they'll want to make it impossible.
If the Mac Pro satisfies those workloads now Apple is free to make the T2 chip mandatory.
I don't think even Apple can afford to buy too many of the Mac Pro. :)
In all seriousness, the Mac Pro doesn't make a good server (for most purposes). Most servers don't need GPU, no server needs a way way overdesigned and expensive case. Don't need the expandability. Etc.
[0]: https://news.ycombinator.com/item?id=18114712 [1]: https://support.apple.com/guide/security/mac-computers-apple...