Originally posted by Rondec Pixel shift is a gimmick at this point. Yes, it does allow for better product photography, but it is not something that easily allows for real world shots. It has been demonstrated multiple times that using it in landscape shots where there is light wind will produce image with lots of artifacts, albeit with extra detail in the parts of the image that don't move. Waterfall photos with it don't look good. It is useless for hand held photos.
As to the reason for the delay, it is hard to say, isn't it? Either there was hardware issue that wasn't solvable in the time they had, a software problem, some feature that they wanted to be there that wasn't there, the lenses weren't done, or maybe they want the video on this camera to be decent and it isn't yet. Whatever the case, there has been a delay.
People aren't blaming the delay on the 42 megapixel sensor, they are just saying that if Pentax does use the newest sensor out there, then they would be more willing to wait on said full frame camera, whereas, they would be less willing to do so if it were coming out with the 24 megapixel sensor in the D610.
We simply do not know the reason for any delay. I've even seen it suggested that the reason may be because Pentax-made adapters for 645 and old 67 lenses aren't ready yet. The real reason could be almost anything, not even technical but financial or organizational. For example, Ricoh could be waiting to have a new service network fully in place before launching something heavily dependent on "pro" users, if that turns out to be the case. I think one can say that we are mostly all looking backwards over sensors. The D610 and D810 lines may well be refreshed with newer sensors during 2016, as may the two mainstays of the Canon range, the 5D Mk III and the 6D. Any Pentax FF camera which came out with a sensor which has been out there for two years or more already would be considered old hat and gone by the end of 2016, which means that Pentax would probably have to drop the price of their new flagship camera faster and more deeply than they'd ever want. So a new-gen sensor is kind of unavoidable whatever the mpx.