Radak #1: The Goyim who will come to bow every month or every Shabbos, they will go outside Yerushalayim to Emek Yehoshafat to see the bodies of the camp of Gog and Magog who sinned against Hashem and intended to oppose Him and exile Yisrael from their land. This will be close to the day of Mishpat. Even though Yisrael will bury them - "u'Kvarum Beis Yisrael Lema'an Taher Es ha'Aretz Shiv'ah Chadashim" (Yechezkel 39:12), perhaps the Goyim will see them during those seven months.

Radak #2: This refers to the day of Din against sinners of Yisrael. Tzadikim will go from Yerushalayim to Gei Ben Hinom and see the Mishpat of the sinners.

Radak #3: This refers to after Techiyas ha'Mesim. Also the Resha'im will waken for eternal shame, like it says "[v'Eleh la'Charafos] l'Dir'on Olam" (Daniel 12:2)

Rashi, Radak #1: It is a worm that consumes the flesh [of a Mes].

Radak #2: This refers to their bodies ¹ - "b'Figrei ha'Anashim."

Radak citing Targum Yonasan: It is the Neshamos of Resha'im. (They will be judged permanently in Gehinom.)

Rashi: It is the fire of Gehinom.

Radak #1, Malbim: It is a sign [Malbim - to recall their evil]. Also their worm is a sign - it will not die due to the fire!

Radak #2: This hints to the Neshamah when it separates from their bodies. If it will not merit to ascend to angels of Kel, it will remain by balls of fire.

Rashi: Is an expression of disgrace.

Rashi citing Targum Yonasan: This is like two words - Dei Re'iyah, until the Tzadikim will say about them 'we saw enough.'

Radak #1: It is abomination, like "l'Dir'on Olam" (Daniel 12:2). The Goyim who will come to bow to Hashem, when they will see the dead bodies full of worms eating them and fire burning them, they will abhor them. They will need to go away, for they cannot bear the stench.

Radak #2: It is a worm. Parah (9:2) says that if Dirah or Kinah of grain fell into Mei Chatas, the water is Kosher, for these [worms] have no moisture.