Radak (17): Until this verse, Yonason translates every "Etz" as Lucha (wood). Here, he translates it as Shevet.

Harchev Davar (Bereishis 50:23): This Nevu'ah was after the 10 tribes and Malchus Yosef ceased! Rather, it refers to the power of Torah in Yehudah, and of Chesed in Yosef. Regarding Etz Yehudah, it says "Bnei Yisrael Chaverav", and regarding Etz Yosef "Beis Yisrael Chaverav", for more are drawn after the power of Chesed than after the power of Torah. Alternatively, Bnei Yisrael refers to the males, and Beis Yisrael includes females ¹ , for Chesed applies also to them. In the future, all will recognize that the power of Shevet Yehudah is proper to rule over all of Yisrael; they will not be divided into two kingdoms.

Radak: I will put Shivtei Yisrael, with Shevet Efrayim, with Etz (Shevet) Yehudah.

Malbim: I will put Yehudah under the leadership of Mashi'ach ben Yosef (refer to 37:19:3:3).

Rashi: They will no longer be two kingdoms.

Malbim: Chazal have a tradition that first Mashi'ach ben Yosef, from the 10 tribes, will stand and fight wars. All of Yisrael will gather under his banner. Afterwards Ben David will come and rule over them. The first Mashal (Etz Yehudah and Bnei Yisrael Chaverav) is for the unity of Yisrael under Mashi'ach ben Yosef. The Etz of Yehudah and Chaverav represents the joining of Yehudah and Binyamin under Zerubavel in the days of Koresh. They became one nation during Bayis Sheni. Even after the Churban, they were united and hoped for redemption. The second Mashal (Etz Efrayim and Beis Yisrael Chaverav) is for the end of days. Mashi'ach ben Yosef will gather the 10 lost and cast-off tribes; they will be under him. Afterwards, also Yehudah, who were already gathered, will unite with them under Mashi'ach ben Yosef, via Hashem's miracles.