Zen is going to be tock, tock, tock...Though AMD has never taken the time to formalize it, a three- to four-year lifespan for its own CPU architectures is about average. For example, the K8 series architecture debuted with the Opteron and Athlon 64 in 2003; with 2007’s mobile Sempron, the K8 trickled out. The K10 series lasted from about 2007 through 2010.
AMD’s last Bulldozer architecture debuted in 2011 and persisted through the Piledriver, Steamroller, and Excavator updates. If Papermaster’s words are to be taken literally, it seems AMD plans to iteratively improve its Ryzen chips through an additional three generations, about one per year.