Intel's Michael Vollmer revealed in an interview with PC Games Hardware that game developers will start to take advantage of ray tracing with two to three years:
PCGH: Are there game developers that already want to work with Raytracing?
Dr. Michael Vollmer: We keep in touch with companies all over the world - I dare say that in two to three years time we will see something. There already are some individual approaches, especially in the science sector, which show that Raytracing algorithms are scaling very well with the numbers of cores. But the migration to a new programming technology takes years; Raytracing is still in an early stage.