There is a constant clammer for sensors with more megapixels. I have been investigating this lately. The common standard for the most detail a person can see in a print is 300 dpi when the human eye is one foot from the print. The Z8 and Z9 produce files which are 8256 x 5504 pixels. At 300 dpi this equates to a print 27.5 inches by 18.5 inches. You cannot look at such a print with your eye one foot away because your eye cannot see the whole print at that distance, you have to back off to see the entire image. It is also commonly said that when viewing distance is considered printing at 200 dpi yields an excellent print because as you back away to be able to see the entire print your eye is no longer able to distinguish 300 dpi. In other words, 300 dpi contains details which the human eye cannot see at the normal viewing distance for a large print. Z8 and Z9 files printed at 200 dpi yield a 41.3 x 27.5 inch print. Many people say it is basically impossible to distinguish between a print at 300 dpi and one at 250 dpi even when examined with the eye one foot away and at 200 dpi when viewed at normal viewing distance for a poster size print. So basically, our current 45mp sensors are good enough for printing large. The "need" for more megapixels, such as a 60mp sensor we are likely to get in a Z7III this year, is generally not really a need for most of us. I should also note that if you process NEF images from Nikon's lower megapixel sensors in Nikon's NX Studio that software has an option to save them at 8256 x 5504 pixels so Nikon NX Studio can transform 24 mp images into 45 mp images automatically. I have done this frequently and have not detected a loss of image quality. (An example of NX studio taking a 12 mp D2x image to 45 mp will be posted below for your examination.) So basically, all current, and even older, Nikon bodies do allow for printing large.
But what if you wanted to print really large, like 5 feet by 4 feet, normally thought to be only medium format territory? Or said another way, do we need to purchase a 100 mp medium format digital body to print larger than poster size? I conclude the answer is no. Modern upscaling software, such as Topaz Photo AI can upscale the pixels in a file to print much larger. To prove this I took a 8256 x 5504 image which contains both sharp detail and bokeh and upscaled it two times to a 16,512 x 11,008 pixel image and saved it as a 53.3 mp jpeg file. At 300 dpi this file will print to 55 x 36 inches or 4.6 x 3 feet. Printed at 250 dpi the file will print at 66 inches by 44 inches or 5.5 feet by 3.7 feet. When printed at 200 dpi it will print at 82.6 inches by 55 inches or 6.9 feet by 4.6 feet. Basically, you should shoot a 6 foot tall person and print that person life size and the image would be sharp at normal viewing distance. Amazingly, we can now use a Nikon Z8 or Z9 and software to do what Richard Avedon did for his In The American West series using an 8x10 film camera! It should be noted that this is just a conservative 2x upscale by Topas Photo AI and that software can upscale larger. If you want to print life size at 300 dpi you can use Topaz Photo AI to upscale more than 2x and I think the results would be just as good going to 4x. Here is a link to flckr where you can examine the 2x upscaled file for yourself. it was shot at ISO 800. Click the image below to go to flckr and view the original 2x upscaled file to examine the detail.