Bump it in source to 2.19.4 immediately, and then to 2.20.0 as soon as there is code that requires a minor version bump, then to 3.0.0 as soon as a major versio

Bump it in source to 2.19.4 immediately, and then to 2.20.0 as soon as there is code that requires a minor version bump, then to 3.0.0 as soon as a major version bump is required. Then your version in source is always semver compatible vs by definition being off until you cut the next release as soon as you introduce a breaking change.