The Decepticons did not discuss the change in Megatron. They didn't dare. He had always been a dangerous, ruthless leader, but since their arrival on Earth he had become dangerously unpredictable. At times he would be incredibly bold, then others far too cautious, pulling back when there was only a hint the tide was turning. He embarked on schemes that almost seemed mad, far too grandiose for a Decepticon leader...
If anyone had been saying such things, Megatron would have killed them.
As Megatron strived to lead the Decepticons, something ate at him deep inside. He could not identify the source of discontent, could not identify what was wrong, but it ate at him like a cancer. He found himself fighting desperately against the Autobots, FEARING them in a way he could not explain even to himself.
Finally, searching within himself Megatron found the answer: someone had violated his spark. Some lesser being had actually touched his spark with their own, tainting him. Worse, Megatron got the sense that, somehow, this other spark was from the future. And with that, came a damning insight...
The Decepticons were going to lose.
It wouldn't be now. And he hoped it would not be in his generation, but he knew with a horrifying certainty that the Decepticons were going to be defeated. Someday they were going to fall, and worse there would be 'peace.' Once proud Decepticons would actually serve beside Autobots. Even work together with their natural enemies! The thought filled Megatron with horror. He would do anything to stop it.
"Decepticons!" Megatron cried, "Attack!"
Notes: I always wondered if there were would be any long term effects from the Beast Wars characters sharing sparks with their Generation One counterparts. In this case I'm assuming both carried away a slight knowledge of the future, not enough to change things, but enough to influence them both.