Jacob is still speaking of things that are to come, but the subtext continues to be that they have application to things that are. Thus, when future Israel hardens their hearts against Jehovah, they will be smitten and afflicted. The promise of the land is that the Nephites will prosper, but only if they keep the commandments. If they harden their hearts, they lose that protection. They too will face being smitten and afflicted.
The point of the story of the future is that there is hope in repentance, and that a final gathering to the full benefits of the house of Israel lies in the future. Nevertheless, the key to the final gathering is coming to the knowledge of their Redeemer, or the atoning mission of the mortal incarnation of Jehovah himself.
The likening to Jacob’s audience would have been clear. They too were on a path of rejection of their God, and that rejection would deny them Jehovah’s protection. Their ultimate gathering would be upon principles of repentance.
How did this happen so quickly in Nephite society? The answer is the large number of indigenous peoples who had joined with them. This is not a sermon preached to Sam, or Joseph. They were faithful. It is a sermon pointed to those who had converted to Jehovah’s religion, and perhaps had either not fully converted, nor had brought with them beliefs that were difficult to jettison. It was that larger population that would be at the heart of this issue.
However, that would also place them in conflict with the faithful who descended from Lehi. Thus, this population consists of the lineal house of Israel, and gentiles adopted in. Jacob is preaching a sermon to unify those two factions.