In the fourth year of Yehoyakim, Nebuchadnezzar comes to power.
Now Jeremiah's predictions are indeed transpiring.
We see a double prophecy:
1. The promise of the destruction of Jerusalem, and the ascendancy of Babylon for 70 years
2. The theme of the "poisoned chalice" which will be drunk by Jerusalem, but then will be fed to all the nations around as God "summons the sword against all the inhabitants of the earth."