I don't see the need for a RED competitor in 2018 because the UM46k is already a strong competitor image quality wise.
My guess is that BMD will build on the URSA Mini and its sensor and will improve that design further.
For a hypothetical UMP MKII I could realistically see a further improved sensor with maybe 6 dB less noise, an option to do in-camera NR, higher frame rates like 120fps in full raster and 240fps windowed, slightly improved DR of ~ +1 stop, improved calibration methods, an improved debayering algorithm with better anti-aliasing and moire suppression. I could imagine a slightly redesigned camera body with the bigger LCD of the UM46k, with more brightness for better in the sunshine readability, some tweaks for buttons and switches alignment, a function wise more useful side handle grip, maybe additional support for the next generation of CFast: CFexpress (v1.0 ... 1970 MB/s up to 7880 MB/s). Maybe a bigger internal buffer for a few seconds of pre-cache-recording and a few seconds of highspeed fps in burst mode. They are certainly trying to get global shutter working with the next gen - but who knows.
And of course some further refining of the camera firmware.
That would be my prediction for their next camera. I don't see them working on a 8k version yet as that wouldn't make much sense at the moment (in my opinion). That could be in the MKIII then.
Of course Grant Petty and his team might have some crazy ideas in petto I am not even dreaming about