Remember when Apple used to make printers?
IDK, I think maybe in december Apple will sell a 4K display in store/online at the time of Mac Pro availability, but, maybe not their own brand, that black Sharp monitor looked nice in the event vids.
But, the currently display may or may not see an update by end of year.
Apple isn't in the monitor business, just like they never really were in the printer business. In the sales business it's what's called an amenity to offer it, adds to the sale of a mac mini, but, not necessary.
The computer hardware and software are what make the Mac Pro, the monitor is neither here nor there (you can get a quality monitor from several manufacturers that specialize in such.) So, if Apple makes it, they will have one 4K monitor, and perhaps an updated 27" display that shares main parts with iMac...they won't be going back to offering several monitors as consumers use laptops and tablets more than desktops these days anyway. The 4K display & Mac Pro are for a more specialized professional computer user.