Hi! As Thunderbird 60 is still available in testing, torbirdy should be able to migrate there. This way, upon updating to TB68, users will at least get a warning that torbirdy is not compatible anymore instead of having the package removed automatically, and maybe falsely assuming that they are still using Tor when sending emails, which could compromise privacy.
When Thunderbird 68 has finally migrated to testing, we can proceed to remove torbirdy from the archive. If you have better ideas on how to do this, let me know. -- ulrike