Honestly, after having The Fallen (who was essentially a god) in ROTF, it would make sense for them to go bigger and badder for the next film. I think a lot of us thought that meant Unicron would be in TF3. I know he was thought about early on in TF3's development, like right after ROTF's release. Looking at how DOTM turned out, it's obvious they went down a very different path than including another god-like Transformer in the film. Does anyone have any ideas, or know why Unicron wasn't in the (supposed) final Transformers film?