Silicon has reached it's limits and competition is mostly in mobile. We'll see big jumps in performance with newer technologies, starting around 5 years from now I think. There's a lot of applications that need 100x faster compute, like advanced AI and genetics. Even mobile computing is going to drive faster performance soon when 5G needs crazy fast CPUs to process large RF bands and synchronize millions of devices in our every day lives. Really we're in the dark ages of performance - once germanium and graphene replace/augment silicon we're back to the 80s and in months stuff will get obsolete.
Mostly the reason to upgrade from an 1st generation i7 to a Haswell or Skylake has been chipset features. PCIe, USB, and SATA have advanced quite a bit even if single threaded performance is barely 30% faster.