Most digital cameras from the 2000s and 2010s are equipped with an optical element called an optical low-pass filter (OLPF), also known as an anti-aliasing (AA) or blur filter. As the name "filter" suggests, this optical element filters out some information coming from the imaged scene.
Canon has applied for a patent that would allow a camera to use its in-body-image-stabilization (IBIS) to approximate the effects of an anti-aliasing filter. The idea is similar to how sensor-shift multi-shot works, but in reverse.
Some cameras on the market these days leave out the traditional optical low pass filter (OLPF), also known as the anti-aliasing filter, to increase sharpness at the expense of increase moiré patterns. If you're not sure what exactly this trade-off is, check out this 10-minute comparison video by New Zealand-based wedding photographer Richard Wong.
There are two ways to look at an incrementally improved DSLR: either the company missed an opportunity to improve something that has fallen behind the industry standard, or they are leaving well enough alone and not 'fixing it if it ain't broke,' so to speak.
Nikon's replacement for both the D800 and D800E, the D810, falls into that latter category: an incrementally improved DSLR that probably won't receive too much flack for it.
When Nikon released its D800E and D7100, people were surprised to learn that these models did without the optical low-pass filter (AKA the anti-aliasing filter). The resulting images from these cameras were sharper, but more easily fell pray to moire patterns in certain situations -- in other words, it was a tradeoff.
But Nikon would like you to have your cake and eat it too, at least according to a recent patent the company filed with the Japanese Patent Office.