I think that it bears repeating again: It's pretty obvious that Apple no longer views the entire Mac line as something for consumers to purchase. Apple views the entire Mac line as a corporate product that they'll also sell to consumers if you're willing to pony up the money
You start with the T2 chip in everything (which is definitely an enterprise corporate feature), and then add 10G ethernet support, small and fast storage (fits with the typical corporate networked workflow), replaceable memory, and then the pricing being in the typical corporate desktop range
Apple has deliberately segmented their market into Mac = corporate/enterprise/professional and iOS = consumer
As for how long the Mini has to live, let's just say that corporate mac sales are very heavily tilted to the laptops.. I'd say there's a very good chance that this is the last one
I think the more interesting question is how long the Mac line will live. You add mouse + monitor + storage support to iOS, then my guess is that Macs will quickly move up even more in price and have the number of models quickly shrink. Not a deadline cutoff, but a forced shrinking of sales until it becomes not worth their while anymore