"It's certainly a possibility," he didn't sound very convinced though.

"But Optimus being here may very well be enough of a reason for Megatron to remain. From what Optimus Prime said, Megatron knows about Unicron as well. If he is plotting to utilize Unicron's powers for his own ends, and succeeds before Optimus can find a way to stop or destroy Unicron, I've no doubt he would use the 'Chaos Bringer's power to wipe out the Autobots."