Is the punishment of the wrongdoers delayed until the Day of Resurrection, as implied by His Almighty's saying: "And never think that Allah is unaware of what the wrongdoers do"?

It is not necessary for the punishment of the oppressor to be delayed until the Day of Judgment. The oppressor may be punished in this world, given respite, and then seized with a severe grasp, as stated in the noble Hadith and the Quranic verses that mention swift punishments for oppressors. This is part of Allah Almighty's wisdom, so that all people would not perish if they were swiftly punished.