Hi,
the export of unsubscribed users will not be probably implemented in version 7.0, but this functionality can be implemented easily in version 6.0. The workaround is to use custom table module for this.
1. You could modify unsubscription web part in way, that for each user who uses it, will be created a record in a custom table.
2. To create a custom table record you can use
custom table API.
3. In custom tables in export already available.
We can also create a knowledge article about this, but it is quite easy for implementation. Let us know if you need further help.
As for import functionality. I created a requirement to add this to the next version. In the current version there Import Toolkit utility which supports import of multiple objects (from .csv file as well). Unfortunately, subscribers are not listed in it.
Best regards,
Ivana Tomanickova