And in the long term?
We envision 2.1 as our last major update of Factorio, and we will shift the focus onto long term support. So things like bug fixes, platform support/compatibility, modding features, etc. Other than that we feel we’ve reached a good place to conclude the active gameplay development.
Aside from the other answer, the article also says they’ll still provide “long term support” which includes modding requests. So even if something is missing for modding, they may still add it.