Last decade Intel adopted a "tick-tock" strategy for its processor lineups, this basically means that every tick represents a shrink of the previous architecture while every tock designates a new processor architecture. It seems NVIDIA took a cue from this by adopting a "ping-pong" strategy to make its Tegra lineup more predictable:
In accordance with the “ping-pong” strategy, the top-to-bottom evolution of each Tegra system-on-chip will take two-years. For example, the company may change CPU architecture and fabrication technology, but retain graphics architecture. Or switch GPU type as well as manufacturing process, but retain general-purpose core architecture. However, if Nvidia introduces a Tegra chip, in two years the company will launch a new SoC with made using a new process tech and featuring different CPU and GPU engines.
For example, Nvidia’s code-named “Parker” system-on-chip due next year will feature the company’s improved “Denver” general-purpose cores and will be made using an all-new fabrication process featuring FinFET transistors. However, the chip will continue to use “Maxwell”-based graphics processing unit.