There are techniques you can do with ray tracing that can't (efficiently) be done with rasterisation, and as the amount of hardware ray tracing power increases,

There are techniques you can do with ray tracing that can't (efficiently) be done with rasterisation, and as the amount of hardware ray tracing power increases, it will make increasing sense to ditch the extremely complex rendering pipelines we have now and just do (relatively) simple ray tracing. Eventually desktop GPU drivers will emulate "old" rasterised games on ray tracing hardware.