Although we do not plan any "big" new features, we are still supporting it will keep supporting it in the future, e.g. we have released new versions for Boxcryptor Classic ~1 week ago (Windows) and ~4 weeks ago (Android).
When using both products, Boxcryptor or Boxcryptor Classic, encrypted data is ALWAYS only be accessible by the owner with the correct password. The major improvement regarding Boxcryptor Classic is that Boxcryptor now has a sophisticated key management for easy collaboration and other advanced features. However, it is important to note, that Boxcryptor's key management is designed in such a way, that we are still a "zero knowledge" provider: Although keys are stored on our server, private keys are encrypted with your password on your client device before they are transmitted to our server. It is not possible to use them without knowing the correct password (which only the owner does).
We have curated more information here: https://www.boxcryptor.com/en/technical-overview