How did he see this?
Rav Sadya Gaon: He contemplated.
Metzudas David: He saw with his eyes.
Who are "Kol ha'Chayim"?
Rashi based on Koheles Zuta: Kol ha'Chayim is Dor ha'Mabul, about whom it says "mi'Kol ha'Chai 1 " (Bereishis 6:19).
Ri Kara: They are those who abandon the old foolish king, and go with the young Chacham, who becomes king in place of him.
Rid: It is this generation.
Seforno: It is people who engage in [worldly matters] Tachas ha'Shamesh. They are drawn after the counsel of a young Chacham with proper reasoning.
Metzudas David: It is those who go Tachas ha'Shamesh - they go diligently and zealously in the world.
All who will be subjects of the second youth 2 .
This verse refers to the animals! Even so, our verse says "Kol ha'Chayim" to hint to the generation in which "mi'Kol ha'Chai" was said. (PF)
Who is "ha'Yeled ha'Sheni Asher Ya'amod Tachtav"?
Rashi: It is Noach and his children, who survived from Dor ha'Mabul.
Ibn Ezra: It is the young Chacham, who ruled in place of the old king. He is called Sheni, for he was a youth and came after [the first king] and ruled in place of him.
Ibn Ezra (16), Rid: It is the children of this generation, who will stand in place of their fathers.
Rashbam: It is the son of the old king, who became king in place of his father, and he is a Kesil, like his father. Therefore, he is called Sheni.
Seforno: It is a young Chacham with proper reasoning. In investigation, he is below the level of the young Chacham with reasoning mentioned above (the young, poor Chacham - 13).
Metzudas David: It is the son born after the poor youth who saved himself with his Chachmah, and emerged to rule. I assessed that he will be king after the first youth that will replace the old king, for I see that the Chachmah of the diligent and zealous is nothing compared to [the latter's] Chachmah.
Refer to 4:15:2:6*.