There is an intention to have a roughly 6-month release cadence from now on.
0.C to 0.D was painful ( 4 years or so! )
0.D to 0.E will be less painful.
Do not base your contributions on what may or may not be stable in the near future, if a feature you are working on is considered too risky when it comes time to a new stable release, it will be frozen and then applied to the new experimental version afterwards.
Just contribute what you want, and the maintainers of the repo will decide when and what a stable version is.