Hmm, I don't have access to that kind of device, but if you're willing to help us test we can find out! Are you a DQ2 alpha backer or alternatively, a testing volunteer?
Basically, the core game engine has a flexible resolution switcher that can go to "any" resolution, including whatever the fullscreen is. The master assets themselves top out in detail at a hypothetical resolution of "1200p" (ie, exactly twice the vertical resolution of the original 800x600 game, but in a 16:9 aspect ratio).
In theory things will still scale past that point, they'll just be a bit blurry, but the pixels will be so small at that point from the ultra high resolution I doubt the eye would really notice.
Text and user interface is based on "points" which scale with the screen. So when I say a font is "12 points" it is 12 pixels tall at the lowest resolution, 600 vertical pixels. So after that, it scales proportionately. So at 1200 vertical pixels a "12 point" font is 24 pixels tall, etc.