When I started as a professional photographer we used film (remember that?), I had a 35mm outfit, a medium format outfit and a 5x4 outfit. Camera bags were heavy (Hasselblad, 3 lenses, 2 backs and a Metz flash is no lightweight option!). It took time to develop film in smelly chemicals and "spotting" prints was a necessary pain. Long print runs (say 100 prints of the same picture) meant careful monitoring of the developer and retouching was an expensive luxury. Then came the DSLR - wow! It was amazing because it made life easier, faster, lighter and altogether more efficient. Some had to be dragged kicking and screaming away from their film cameras - seeing any similarities here? Now film is mostly for bearded hipsters and a few students it seems.
A lot of us humans are slow to adapt to change. Many are comfortable with the familiar. I think that perhaps there will always be a small market for the DSLR, after all, the Victorian painter Paul Delaroche famously cried “At this moment, painting is dead” when he realised the potential of photography and yet we still have people buying paint and canvases today. Anyone seen a cheap Picasso for sale? There may be fields where the DSLR is better for some reason for a while at least.
For me the present and indeed the future is mirrorless. Now that the likes of Nikon and Canon have finally awoken from their slumber and are taking mirrorless a bit more seriously, the end may well be nigh. Their rumoured full frame cameras will set the date (dependent on their sales), but I think that just like the TLR camera was succeeded by the SLR, the DSLR will be succeeded by the mirrorless. The date that perhaps the DSLRs will rest in peace may be pretty soon, maybe 2020? I think that Paul Delaroche (if he was still around) might then say “At this moment, the DSLR is dead”.