Re: Zen 2?
Not to mention that they need to test, evaluate, sign off the design and order the components before they start building the kit for consumers. That's without considering test rigs needed to be available to the games developers to code against (although I'm assuming they could be a bit less refined).
There's always a line to be drawn to determine how new the kit can be. Newer generation ones will hopefully be able to run a bit cooler as CPU/GPU tech advances and desktop/living room footprint will shrink.