Historically the mass of cameras have been to fairly casual photographers and that market has definitely swung to cell phones, decimating the traditional small-sensor point and shoot - the 1" sensor P&S are holding some ground but they also shoot high definition video, so that has spread the load. Canon has dominated the low end DSLR market pretty much since the inception of the Rebel or 300D models.
From my own research some of that market is swinging to the very small form factor 1" group, and some has gone to high-end cell phones. That leaves us with enthusiast and professional-level purchasers. I think both groups are holding on to their higher-end DSLRs and lenses, but they will not be turning their kit over as quickly as the lower end market - the equipment is better made and more expensive. However mirrorless MILCs are now whittling that population down and I would expect as newbies come into those two groups they will generally take to MILCs. Older folks like me will likely keep their DSLRs as long as they can carry them. Yet I think with the vast number of DSLRs and lenses on the market a generation of users will use these until they can afford the latest tech. Of course there will always be the enthusiasts, like those who shoot 8x10 glass plates or 35mm film!
Right now, professional sports and action photographers are still using DSLRs and those big lenses, and will do so until a practical (and economically viable) selection of MILC bodies and lenses come to market. Hence the release of the EOS 1DX III and the forthcoming Nikon D5.