Optimus comes home.

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Well, I wouldn’t say his time with the Decepticons was ALL bad. In fact, while staying with the Autobots, some familiar faces may turn up at the Autobot base now that Starscream is hanging out there!

For a lot of people, the war has essentially been over for nearly three years (due to both Optimus and Megatron being out of the picture). Now that Megatron is back, not everyone wants to go back to war, and some of the Decepticons that had been hiding out on Earth are starting to reach out for help. I think with Starscream staying with the Autobots, he'd become a sort of liaison between ex-Decepticons and Autobots. This isnt to say they're all living at Autobot base now, some of them might, while others like Swindle are out doing their own thing and only showing up to trade or whatever else.