There's a very big delay between finalizing a design and actually etching said design in silicon, and bringing a design to silicon of course involves a lot of non-trivial work. This is kind of why Intel had the whole tick-tock thing, as whilst the current design is being put into silicon, the design team can work on the next iteration of the design.Also why AMD could be very confident about their next Zen iteration being a lot faster when they were releasing Zen 2.