So, if you don't print very large and under extreme lighting conditions you don't need to upgrade. So market is a bit saturated.
But, my guess is that camera manufacturers need to adjust to falling sales, the boom is over.
I agree that the boom is over for dSLR's but I reach further back, as in about 30 years, for the roots of the boom and the fairly quick onset of its demise.
Back then (the good old days?) anyone with sufficient limits on their credit cards could buy gear the manufacturers assured them was pro quality, and that they could make their fortune selling "nature" to magazines, stock houses, etc. Every Tom, Dick, George and MaryAnne was buying film cameras to get in on the rush, and with the rapid emergence of digital, of course they had to upgrade to keep pace with the market.
Trouble was, very few could manage to sell anything at market rates, so they started discounting, and ultimately giving away their photos "for exposure and market presence." Meanwhile magazines were dropping their rates, as were any other businesses who could get away with it. With the explosion of the internet and the ease of uploading digital images, enterprising businesses (ad companies, publishers, small businesses, etc) could find free photos and folks happy to give up their rights for that magic market exposure.
I bet something north of 95% of those same happy hopeful nature snappers have now switched to a pocket camera, or more likely a smart phone. They're taking photos for their own pleasure and especially for "sharing with online friends" rather than sales dreams. With the younger generation (emerging market?) in particular, it's all about the ever-present smart phone. Why spend money on a dSLR when they have a great camera at all times in their hand or hip pocket? For evidence, visit any national park and keep tabs on the cameras actually in use. Back about the time dSLR's were really catching on, you were NO ONE if you didn't have something big and black hanging around your neck and a monster bag at your side. Today in the same venues I'm surprised, even startled, to see ANYONE with a pro-grade dSLR. It's mostly smart phones, a few tablets, and even fewer pocket cameras.
In spite of what we think of ourselves as cutting-edge artists and even pros, we in fact constitute a very small and shrinking market segment. Manufacturers need to sell to the biggest markets and they'll put their innovation and marketing efforts into competing for a segment of that market. I've never seen a number and Nikon certainly won't share (nor would any other manufacturer), but I really wonder how many pocket cameras they sell for every dSLR. I bet it's thousands.
As we strive for the very best gear for large photos in challenging light, we constitute a very small percentage of their sales. Are they going to continue dumping huge R&D $'s into keeping up with our needs, or are they going to divert the R&D $'s to products for the highly competitive non-dSLR market? I wish I had asked for a card or could remember the guy's name who I talked to at the Nikon booth in a recent show. He was succinct, if also smilingly curt: "In today's market pixel peeping is so much navel gazing."