CustomPC had an interview with Daniel Pohl, Intel's ray tracing expert. Here's a snip:
CPC: Nvidia’s chief scientist David Kirk says that ray tracing will be another tool in the developer’s toolbox, rather than taking over completely from rasterisation. Do you agree, or do you think that ray tracing will end up taking over in games in the long term?
Daniel: Looking ahead five to ten years from now, I believe that rasterisation will be used less and less in games, and will instead be used in combination with other algorithms.