Mormon has paused in his historical descriptions to address those to whom he is writing. This comes after he has declared that he no longer believes that he can do anything for his current people, therefore, his thoughts turn to future generations that he might be able to help, and help avoid the fate awaiting his own people.
This is not the end of a chapter in the 1830 edition of the Book of Mormon. Thus, this statement is an aside in his historical narration and not yet a final declaration. That will come, but will come in our Chapter 7.