I saw there was another thread regarding expansion. Myself I have been experiencing a string of surprisingly peaceful games since I patched up. Partly I have adapted to the new amounts of troops the AI produces I guess, so they attack me less. But they don't attack each other either. Which is a bit boring :/
Emperor. Perhaps the lowered trade-thresholds have increased their trades and thus the 10-turn-peace-agreements. Or maybe I just had a string of randomly very peaceful games. Yesterday I finally saw an inter-AI war though. Or maybe it is just me surviving and thus haveing the time to watch the AIs more carefully.
The AI seems very unpeaceful to me. They attack other civs (player or AI) quite freely. They also invite other civs to declare war, which tends to cause conflicts to erupt into major wars. Maybe you've had some games where everyone has been roughly even? The AI does like to put off initial war declarations until it has an advantage.
Ah yes, the AIs and myself have been unusually even score-wise these games. That is probably the answer then, perhaps an unintended consequence of an overall better AI