Did it ever occur to you that some people game on 120 or 144hz monitors.
Most modern at least the highly threaded ones respond more to the number of cores than the core frequency. Games like BF3 and BF4 are examples of this, with at most 5 fps apart when using the same GPU.
Its really too early to call this as we have no idea what Nvidia response to Mantle is going to be. The rumor mill suggests that the next Nvidia GPUs (Maxwell) are going to have an ARM co-processor to offload tasks from the main processor. If the rumors are true then both companies have been focused on eliminating the CPU bottleneck when using their GPUs.
Its going to be an interesting 18months to see where this ultimately settles at. My early guess is that depending on performance this could cause a price war between the two GPU companies. This all depends on how many Mantle games are announced and get released in that window as well.