Update: More complete data is now available. The finale actually garnered 4.215 million adults 18-49, which translates to a 3.3 adults 18-49 rating.
The series finale of Sons of Anarchy was watched by 6.4 million viewers and 4.2 million adults 18-49,
which translates to a 3.2 adults 18-49 rating. Both numbers are series highs, narrowly beating the season premiere which earned 6.2 million viewers and 4.1 million adults 18-49. Your predictions were too optimistic.