I've been keeping up with Apple since 2004 when I was in high school. Even back then, a lot of Mac fans wanted Apple to release an "xMac": a Mac with one or two expansion slots, user-serviceable, and priced less than an entry-level Power Mac G5/Mac Pro, somewhere in the $1,499 range. Yet Apple never delivered. Sure, the Mac Mini was introduced in 2005 and has remained part of Apple's lineup ever since, and there's also the 2013 Mac Pro and the modern Mac Studio, but these lack expansion slots.
Sadly I think it's even less likely we'd have something like an xMac today. Consider the MSRPs of base-level Mac Pro models from 2006 onward. During the cheesegrater days, entry-level Mac Pros were available in the $2000s. The "trash can" Mac Pro had a starting MSRP of $2999; more expensive than the cheesegrater models, but still not a gigantic leap from its predecessor. But when Apple released the 2019 Mac Pro tower, the MSRP took a dramatic leap to $5999, pricing out many people who had the budget for a $2999 or even $3499 computer. As a user of a 2013 Mac Pro, I would've bought a 2019 Mac Pro in a heartbeat in 2019 had Apple maintained a $2999 entry price. The ARM Mac Pro is even higher priced at $6999.
The message from Apple for over 20 years has been loud and clear: Apple does not want to sell an affordable, expandable, user-serviceable desktop, and Apple at times doesn't always look committed to expandability and user-serviceability. I expect the Mac Pro to be unceremoniously discontinued, though I could get shocked like I was in 2019.