I think the Mini and the Mac Pro are going to be discontinued eventually. They are "specialized" products that are sold in numbers that, given Apple's production numbers, are essentially rounding errors. Not trying to be flippant here because I know people love these products, but to me, that's the reality.
As for the iMac, that got updated in June, and the new iMac Pro will be coming out in a few weeks. IMHO, the new iMac Pro will be the replacement for the Mac Pro.
As for displays, Apple is out of that game, just like they are now out of the router business and the printer business (the latter dates me because I fondly remember the Apple LaserWriter series

). Third parties can make these peripherals with excellent quality, so Apple doesn't really need to anymore.