I'd say this depends on how the premium PC gaming market develops. The current 40" UHD monitors are probably meant for either enthusiast use or CAD, medical imaging or other professional non-colour accuracy sensitive applications. These professional fields have nothing to gain from 120Hz. On the other hand, as long as the panels become available (which they might due to the drive for useless Hz bragging rights in the TV field) and display controllers and interfaces that can drive them become widely adopted, there will be little stopping any manufacturer from making enthusiast monitors like this. They will, however, charge a premium. Both panels, controllers and other parts will be expensive for a good while still, and >30" sizes will always be a tiny niche for PC usage (sitting 2' away from a 40" monitor makes no sense in the vast majority of cases). Given the "popularity" of $1000 GPUs I wouldn't doubt that these monitors will be coming, though. People love excess.