@Barhandar
 
I severely doubt that. I’ve been to plenty of conventions (MLP, Anime, Sci-Fi, etc), and there’s always a small number of people who go around just randomly taking pictures of everyone without asking.
 
If it was intended to be a “cosplayers doing things other than posing for the camera” picture, then the photo would be at least properly composed. But since about 50% of the photograph is the floor, and the cosplayers are far off-center, I’m leaning much more towards whoever took this picture tried to do so without anyone noticing.
 
Now, I’m not saying the photographer’s in the wrong for doing so - it is completely legal to take photographs of people in public, with or without their permission (IANAL). Plus if they show up at conventions in cosplay, it’s only natural that people will want to take their pictures. All I’m saying is that it’s very rude to take pictures of people without their permission, and almost always, such pictures turn out very poorly.

@Joey  
It’s not a cosplay photograph, it’s a “these guys in cosplay doing cosplay-unrelated thing”. Entirely separate from permission, which could as well be there.

Optimus prime is relevant no matter what the con

Pro tip - cosplay photographs generally turn out a lot better when the cosplayers are actually facing the camera.
 
Of course, to get cosplayers to face the camera, you do need to ask their permission first, instead of just trying to take their picture without them noticing. But it does have the advantage of being a lot more polite.