As Lehi begins the blessing on the posterity of Laman he reiterates the foundational promise. They will prosper if they keep the commandments. Notice, however, that the nature of the promise is personal, not communal. The penalty is not that another nation will conquer them as in the typical formulation of the promise (such as in 2 Ne. 1:9). The penalty is that they will be “cut off from [Yahweh’s] presence.”
The promise that is repeated among the Nephites is most often associated with the land, not with a person (with the exception of Alma 37:13). The promise to the children of Laman begins with the personal application and does not mention prospering in the land or protection from other nations. Our knowledge of the rest of the Book of Mormon suggests that Lehi prophetically understood that the descendants of Laman and Lemuel would become part of the “other nations” that would invade the Nephites. Thus, for the Nephites, the promise of preservation in the land was applicable, but that promise was not applicable to the future Lamanites. For them, the issue was personal salvation, not temporal salvation.