Doing 8K on FF or small sensor is a whole different story in term of thermal dissipation. Heat is the physical limit at the moment with the current technology (CPU, memory, etc.). See the fan on the SH1 and most pro camera. Agree with the crop, 8k video shouldn't crop much unless they go way beyond the "native" 8k resolution (need a minimum of 40mpx fora  3:2 ratio sensor to output 16/9 8k).