As the pixel spacing increases (sensor resolution decreases), moire/aliasing become more common and serious issues. So far only Kodak made a relatively low resolution 14MP full frame camera (or a few of them) without the optical low pass filter and it got a lot of criticism for the artifacts in images produced with it. The next one with self-cancelling filter setup (effectively similar to no filter) was the D800E (followed by D810, no OLPF) with 36MP. In 36MP FX moire is not too common and people seem to accept it. However, Nikon, Canon and Sony full frame sensors between 12 and 30 MP so far have had the filter in place. I guess the artifacts are just too common with such low resolutions without the filter. 36, 42, and 50 MP full frame sensors with the exception of the D800 have been made without OLPF. I guess if Nikon produces a much higher resolution successor to the D750, then it would likely be without it.
