What will be wondrous in their eyes?
Rashi: The great Chesed that I will do for them.
Rashi citing Sukah 52a: In the future, Hashem will slaughter the Yetzer ha'Ra. Tzadikim will be astounded - how were we able to overcome this great mountain?! Also Hashem will be astounded over this!
Malbim: According to nature, it is impossible to succeed so much, since they are under their afflicters, and all of them prosecute against them.
Why will it be wondrous in Hashem's eyes?
Rashi: How did I abandon the great anger?
Refer to 8:6:1:2.
Radak: This is said in astonishment, as if there is the prefix Hei - ha'Gam b'Einai Yipalei. The same applies to "Atah Zeh Bni Esav" (Bereishis 27:24; it is as if it says ha'Atah).
Radak citing Ibn Ezra: I will do a wonder in those days that I did not do like it [beforehand].
Malbim: Based on the current situation, they should not last long in the land, for they are few and lowly.