This is mentioned in the roadmap - ClassicPress | Stable. Lightweight. Instantly Familiar.
Preamble: The first version of ClassicPress will be a long-term support (LTS) version. If you choose to, you can stay on this version for years to come. We won’t introduce any changes that could break compatibility with themes or plugins that support WordPress 4.9.x.
When I read that paragraph it gave me the confidence to move everything over to CP. 