I don't think the future is just about mirrorless vs DSLRs. That's pretty much a given, it will be predominantly mirrorless - why would you want a camera with a flipping great mirror and costly mechanical shutter if you can produce a better camera, and cheaper, without them? The technology exists, it's just around the corner - a solid state camera with no moving parts
Most buyers don't see mirrorless vs DSLR as we do, it's just a slightly different box that does the same thing.
But the big picture question is more difficult. Smartphones have taken over the mass market, and ILCs (interchangeable lens cameras) currently prevail at the enthusiast and professional end. I'm sure that will continue to be true, but what happens to the huge gap inbetween, where the major camera manufacturers make their money? How will it evolve, how big will it be, and crucially, what products will it need and when will it need them?
Alongside the revolution in cameras is the way we now use images - on-line and on-screen, uploaded to social media. Cameras must be 'connected'. No more prints.
Nikon made a mistake with the mirrorless Nikon-1 series, though it's important to remember that at the time it was hailed a success and initially sold well, particularly in the important Japanese market. Nikon's president was famously quoted as saying he was gambling the company on it, but in hindsight it was less the wrong product at the wrong time, but rather more that smartphones just swept it aside as they continued their relentless march further upmarket than anyone thought possible. And that is at the heart of the conundrum IMHO - where will smartphones end and enthusiast/professional cameras begin?
I suspect smartphones have a lot of development potential to come, with multiple lenses and sensors working with clever software, and capable of doing most of the things we now do with our ILCs. What will be left? Long lens stuff, wildlife and sport, flash and studio work? Not much else, but Nikon is well placed to exploit whatever is left, even if the market as a whole is out of their control.
But is that such bad news? Great images aren't going out of fashion, and the skills needed to make them are still mostly with the photographer. Much as I love my shiny cameras and lenses (and that drives more equipment sales than most on here will own up to) if there's a better way of doing things, I'll use that