Last 5 years they were slacking off, because economically there is no reason to go over the usual 10-15% yearly performance bump. But actually they were accumulating aces up their sleeves. Again, no reason to show your hand, if you don't have to.
But the time has come. Right now Intel has 3 major problems: 1) Meltdown/Spectre situation 2) AMD is awoken from sleep with surprisingly good Ryzen lineup 3) Apple craves new powerful CPUs to satisfy unhappy MacBook Pro customers
Intel can fix all of this with one sweep. Just by releasing a brand new CPU that will surprise everyone. Of course with hardware Meltdown/Spectre fix. They were holding off, but it's time to drop all these hidden aces on the table. And I believe it's gonna happen. Not right now with Cannon Lake, but with the one after - Ice Lake on 10nm transistors, by the end of 2018. It's going to be even bigger than NVIDIA's GTX 1080 success.