We will support upgrades so that you can seamlessly go one minor version up at any time without breaking, but we won't hold an old API version left in the binary more releases than necessary.

Upgrading from v1alpha1 (the only option in v0.4.0) to v1alpha2 was possible in v0.5.0, but is not needed in v0.6.0 anymore as everything touched by v0.5.0 is always at v1alpha2.

Update: We'll remove v1alpha1 from v0.7.0, as that most likely introduces v1alpha3. Maintaining three API versions in parallel would take up too much time/effort. v0.6.0 will thus have v1alpha1 still available (use discouraged).