Radak: When they will leave exile high-handedly, and find even in the Midbar water and all their needs - "Lo Yir'avu v'Lo Yitzma'u" (49:10) - then Kevod Hashem will be revealed to all the nations.

Malbim: In the future, Hashem will be revealed in a way superior to now, in six ways. (a) Nowadays He is covered in garments, walls, clouds and darkness. (b) Nowadays, only Kevod Elokim was seen; this refers to conduct and Hashgachah. Then honor of Hashem Himself will be revealed. Also refer to 40:5:2:2.

Radak: All people will know that Hashem spoke. I.e. they will know that these consolations that the Nevi'im said, they spoke via Hashem, when they see that they are fulfilled. V'Ra'u is knowledge - vision of the heart, like "v'Libi Ra'ah Harbeh [Chachmah va'Da'as]" (Koheles 1:15) and similar verses.

Malbim: This hints to four more ways in which in the future, Hashem will be revealed better than now. (a) Until now, people understood Kevod Hashem; in the future, they will physically see it. (b) Until now, even the Nevi'im who saw Divine images, saw only prophetically. Now, all will physically see His honor. (c) Until now, only individuals understood Kevod Hashem. Now, everyone will, "Ki Mal'ah ha'Aretz De'ah Es Hashem" (11:9). (d) Until now, people did not see at the same level - "v'Nigash Moshe Levado El Hashem v'Hem Lo Yigashu veha'Am Lo Ya'alu Imo" (Shemos 24:2).