Unfortunately I found a bug - checked this when your plugin is activated and deactivated.
When editing a post:
1. Click in "Scheduled for" to set a date
(very cool the date of the latest scheduled post is set automatically)
2. Note the name of the permalink
3. Click on "Schedule" - page reloads
(not sure if it is named like this, I´m using WP in an other language, means the button to publish a post)
4. Now the permalink changed to the one of the last post "-2" is added
So a wrong permalink is saved.
Do you have the same behavior?