We're actually working on many features, not just on static generation.
We strongly believe there are major wins to make in scaling JAMStack and bringing static generation to larger applications in order to allow them to scale even further.
Examples of this are:
Next.js is becoming more hybrid in that you get to choose per-page if you want it to be server-rendered on-demand or statically generated at build-time and then incrementally re-generated.
The incremental re-generation case works for most sites backed by a CMS for example, whereas if you want to make the tradeoff you can move to on-demand generating it for each request.
This allows for full flexibility and you're not tied to one solution or the other, for example you might start with on-demand rendering but then eventually move to static (and vice-versa)