John came to join the others, concluding that this meeting meant that Magneto must have some idea of what they were going to do. Maybe he knew now who did that to Xavier or maybe he knew who he could find out from. Or maybe it didn't have to do with that at all. Magneto kept things close to his chest and Mystique wasn't around all that much, so John couldn't try to see if she was wiling to share. The metamorph was notoriously good at keeping things to himself, so he knew that if Mystique wasn't going to tell him, then he wasn't going to push for answers.
He joined the others and took a seat, watching the numbers of the Brotherhood and seeing people he might call friends and a couple he would refer to as former lovers. Both were strong words for John and might not be the best definition. Regardless, he knew them, and they shared in the same mission and goal that brought them into this room.
He waited quietly because he knew that Magneto would only speak when he had everyone's attention. So John made a point to keep his eyes focused on the old man.