1) Me, I wouldn't consider buying a larger tablet than my current 12.9" iPads. It would become uncomfortable to hold it in a desired position for more than mere seconds, and it would become too heavy for stands when in portrait orientation (my default). YMMV.
2) Ten(?) years ago, there was this huge (19"?) Android tablet by HP or Samsung. Full HD resolution, which was already on the coarse side in that time. Must have been a big (2*) mistake.
3) Whom would a larger (than existing) tablet target? Media consumers would be better served by a separate monitor (or television), and so would drawing artists. (I have always preferred the smallest Wacom tablets in my Windows-only days, in order to have my hand rest comfortably.)
The one group I could imagine is one that I seem the only person to target is: directors of major outdoor engineering jobs, like upgrading railways, Chinese or just European scale. But then, imagine using large tablets at freezing temperatures or in strong winds...