What is the significance of the fact that Hashem will go ahead of them into Cana'an?
Seforno. Hadar Zekenim (in Pasuk 1), Da'as Zekenim and Rosh (both in Pasuk #2): It was to reassure them that they have nothing to be sad about, since Hashem, whose leadership is superior to his, will go with them into Eretz Yisrael.
If Hashem will lead them into Cana'an, what does the Torah mean when it adds that Yehoshu'a will go in front of them"?
Ramban: It means that, although Yehoshua will replaced him as the people's leader, the Shechinah will still accompany them. 1
Seforno and Targum Yonasan: Yehoshua would go at the head of the troops, but under the jurisdiction of the Shechinah, who was the overall commander-in-chief.
Ramban: In spite of the fact that Moshe was no longer there.
