Perhaps it was William Lear (creator of the Learjet) who said something like "you never have to repair or replace anything you leave out".
The Nikon F's, F2's and their lenses are about 40-55 years or so old. A high percentage of these work just fine with little maintenance. They'll probably do so for another 50 years or more. I just can't imagine that in 50 years there will be a fully functioning D4 and, say, a 105/2.8 AF-S VR lens. I don't think even an F6 will last that long.
Ok: 50 years from now, anyone having a fully functioning F6 or newer camera, bring it to me and I will give you its weight in gold :- )
I realize longevity and robustness isn't the be-all and end-all in photographic equipment. They're just tools. I *do* want my images to last, because they are what's important.
I can also appreciate the plastic inexpensive cameras. For nearly 20 years I scoffed at cameras like the Canon Rebel G (100% electronic, autofocus, entry-level camera) and then I decided to try one. It was so much fun and I got good photos. So, one's equipment isn't everything.