SYNC 3 updates will generally be about once a year but may vary based on new features or bug fixes. Maps updates are coming soon(NOT included with SYNC 3 updates.) These will be free for 5 years (1 update per year)
Map Updates (Coming Soon)
That's not for USA/Canada mapping. SYNC 3 was first introduced in a production model in spring of 2015 and only one official user update has ever been released and that was for version 1.X units only. There is no schedule for SYNC3 updates. Though in regards to updates I would suspect they will be more frequent as SYNC3 is now in all models. This is just my personal speculation though.