The DeX already runs a version of Photoshop, and the Samsung store folks were pushing the DeX as an option for website development, especially as their browser supports both desktop & mobile modes. (If I recall correctly, I think he even said the desktop browser has some developer tools built-in, but I haven't been back to the store to check that.)
I'm not certain Photoshop can be classified as general productivity, but if we gave it the benefit of the doubt anyways and further assumed end-users would somehow benefit immensely from such a high resolution, then I'm still not seeing were decent refresh rate fits snuggly into the imperative.
What general productivity task at mobile compute scale would optimally leverage 4K resolution at a decent refresh rate?