"Softproofing" of printed sharpness. I don't care how it is done (actually, I think it is an interesting question, but let's leave that for now). Perhaps it will only be available for special displays (retina macbooks, or connected retina iPads) and selected printers (Epson might be an obvious choice, but I am hoping for Canon as well).
If a given printer/driver/driver setting/paper/ink/... is at all repeatable, then it must be possible (somehow) to measure and characterize it. If you have a display with incredible pixel density, then it must be possible to make some perceptually relevant "simulation" of the printed spatial distribution (no matter how crude, it ought to be better than "not simulated at all")?