Tukulti-Ninurta may have brought the Middle Assyrian empire to its territorial height, but the interal political issues he creates along the way will pull down his rule. After that, Assyria will be mired in a chain of kingly assassinations while the world seems to collapse around them in the Bronze Age Collapse. Meanwhile, Babylon will shake off the chains of Assyrian vassalship, but won't really manage to make good on their independance, getting repeatedly sacked by the Assyrians and Elamites until the final end of the Kassite dyansty. This is the end of Mesopotamian bronze age history, and it is a bit of a mess, but you can be excited for the age of empires that is waiting in the wings.