The prophecies of Micah were delivered during the reigns of Yotam (Jotham), Ahaz, and Hizkiyahu (Hezekiah), making Micah a contemporary of Yesheyahu (Isaiah). Micah was a southern kingdom prophet, originating in Moreshet, and like other southern kingdom prophets (Amos, for example), he was concerned with the oppression of the vulnerable by the wealthy:
But lately my people have risen up as an enemy;You strip the rich robe from those who pass by trustingly with no thought of war.The women of my people you drive out from their delightful houses;From their young children you take away my splendor forever.-Micah 2:8-9
Micah is also interesting because he features in the prophecy of Yermiyahu (Jeremiah). When Yermiyahu was tried for false prophecy, the aversion of Micah’s prophecies is cited in Yermiyahu’s defense. In Yermiyahu’s time, it was accepted (and Yermiyahu did not contradict) that the people had repented the wickedness for which Micah had declared them condemned. Therefore the threatened consequences of that wickedness had been averted. In that sense, the prophecies contained in the Book of Micah have been fulfilled.
However, Micah’s prophecy was the imminent conquest of Yehudah by Assyria and eventual Exile in Babylon followed by a glorious return. According to Yesheyahu and 2 Melechim (2 Kings), Hizkiyahu’s actions resulted in a delay of those events, rather than their negation. Micah’s prophecies were indeed averted, but only for a time.
Because prophecies hinge on the concept of consequences to actions, their fulfillment (or aversion) is not necessarily permanent. All of them are specific applications of the blessings and curses detailed in Devarim (Deuteronomy). When we are righteous we are blessed. When we are unrighteous we are cursed. These blessings and curses (the Covenant) are eternal. Thus an averted prophecy retains relevance in that it may become applicable later if the pertinent behavior resumes. The prophecy of Yonah against Nineveh was averted, for example, according to Yonah, by Nineveh’s repentance, but some interpret that prophecy, not as averted, but as delayed, since, ultimately, Nineveh fell to the Chaldeans.
The prophecies of Micah against the kings of his own time were indeed averted, as indicated in Yermiyahu. Ultimately, though, since the Covenant is eternal, those prophecies regained currency in the generations following Micah’s, and his prophecies were ultimately fulfilled at a later date and recorded by the prophets who followed him and Ezra and Nehemiah.