I would not at this point say that offline support will never be implemented, but this is an option that will need to be carefully planned. The problem is that this would potentionally allow music to bw downloaded and saved locally, and this would not be popular with Spotify. To implement offline support, the audio data will need to be properly secured (encrypted), along with the assoicated decryption parameters. This to ensure that the offline data only can be usedk with the Spotify client and a valid premium account. It is something that needs to be investigated further..