I just can't see any reason for the iPad Air going 3x, (3072x2304) would just impact performance and battery. Now seeing someone found 3x ipad assets in the new beta iOS, this can only be for the new plus or pro 12.9 iPad. No 4x ipad assets so no 4k display yet. That would be a ppi of around 300 for a 12.9 screen, which is better than the iPad Air, and a great starting point and gives people another reason to jump to the 12.9 I think the 12.9 will also be very light and have some new input device for pro artists, and multitasking. And the resolution is certainly going to be 3x.