

The end of DSLR cameras has been coming for some time. Manufacturers have been slowly phasing out their DSLR lens lineups over the past few years and I don’t think Canon or Nikon are making that many DSLRs at this point. At some point it won’t make sense for them to keep the lines around and the stock will dry up.
It was clear around the time of the Sony A6000 that mirrorless would usurp the DSLR in the near future, that camera had already matched much of the performance of the high end cameras. Once the lens lineups were fleshed out more and the autofocus was applied to full frame there was little reason to buy into the older systems.
There are two types of autofocus systems that cameras use, phase detect and contrast detect. Contrast detect is what all point and shoot style cameras (and early mirrorless interchangeable lens cameras) used where they identified contrast of vertical edges and used that to determine if an image was in focus, this is a slow process as the camera needs to figure out what direction to move the focus and check the image at multiple focus positions to compare until the camera determined it was in focus.
DSLRs have a separate sensor up near the viewfinder that does phase detect autofocus, this is different in that it can determine how far the lens is from being in focus and go directly there which makes it significantly faster which was crucial in many professional applications.
Eventually sensor manufacturers figured out how to integrate a version of phase detect into the pixels of the sensor itself. While these didn’t perform as accurately as the separate phase detect arrays in DSLRs, they had an extra trick where they were able to create a hybrid autofocus system that used the phase detect array to get close and then contrast detect to get accurate focus. It was only once this was implemented on mirrorless cameras that the advantages of SLR disappeared.