I'm assuming best blacks come from OLED tech...?
To be clear, there are no consumer OLED panels in existence of the size you want.To be clear... It doesn't have to be 4K. Something less resolution would probably work just fine...
At this point I might suggest just holding off until the rumored 48" model comes out in 2020, it's much more digestible for normal desktop viewing distances. Being that it's identical pixel density to a 24" 1080p panel, just scaled up.just get a wallmount with a 55" lg with Gsync oled. you will not be disappointed, with the right settings there will be little to no worries of burn in. (you dont need 100% brightness 24/7 with no sleep mode)
TCL 8 series is out now, but the smallest is 65".At these prices might as well wait for a mini LED. A CNN logo will burn onto an OLED in less than 800 hours, OLED is really not practical for desktop use unless you want to churn through a new display every few months.