I see three groups of people here: those who take snapshots with little care for quality (cameraphones), those who care about quality but don't want to pay too much for it or have too big a camera (mirrorless), and those who put image quality above everything else (SLR).Not really true any longer.
Many of the mirrorless cameras outperforms anything that Canon offers at the moment. Especially the new A7R from Sony, since it will offer a whole lot more DR and resolution than the 5D3/6D/1DX.
DSLRs still have the upper hand when it comes to lenses, but for how much longer? And besides, the DSLR lenses can be used on mirrorless cameras.