I believe your impression is correct with respect to stability. We might disagree wrt to the nature of the improvement phase, there are some structural changes proposed.
But more importantly, you stumbled upon the point that we have to more prominently communicate the roadmap, or better, the process on how we come to the roadmap.
The next major improvement activity includes an architectural change (also in order to be able to parallelize community activity) and is documented in this GEP:
https://github.com/gardener/gardener/blob/master/docs/proposals/01-extensibility.md
(I can’t find the recording of that session …)
Please state your question again in our next meeting:
https://docs.google.com/document/d/1314v8ziVNQPjdBrWp-Y4BYrTDlv7dq2cWDFIa9SMaP4/edit
Regards, Vasu