Semantic versioning dictates that patch versions (0.6.0
to 0.6.1
) are bugfixes, minor versions (0.5.0
to 0.6.0
) are backwards-compatible, and major versions (0.6.1
to 1.0.0
) can contain breaking changes. However, this only applies to versions >=1.0.0
, which we are not. So:
I assume that standart versioning model applied so change of minor (bugfix?) version (0.6.0 -> 0.6.1 -> 0.6.2 -> etc...) do not break anything whereas changes of major version (0.6.x -> 0.7.x) may break. Is it?
Yes, this is correct. We provide upgrade scripts for all versions, although a minor version bump will mean there are breaking changes that can break plugins that are tied to a specific version.
If there is a specific bug that you would like backported to the v0.6.x branch, please let us know and we can take a look.
We tend to limit the number of backports only because they may introduce regressions, and the branch is no longer in active development. Simply make the case to us and we'll try to backport it 
Edit: c8e0eab34e933ae64178936be5d17fd78b5a9971 has been backported to v0.6.x