It's not a spoiler if it's not true though. By definition spoiling should require that the spoiler in question give away information that is in the manga or something. Things like 'The Sixth Hokage' might be true, but just seeing the title doesn't imply that there will or won't be a sixth Hokage in the story. I don't think the goal of the spoiler rules is to protect people from idle speculation, it's to protect people from being exposed to ideas and having a very strong reason to believe that the ideas will take place in the anime before they actually do.

Example, around the time Sasuke gets put in the barrell if I werer to speculate "I wonder if we'll see Sasuke come out of the barrel and fight before this arc is over" people wouldn't have any reason to believe it was going to happen other than it being plausible. However if I were to say "I can't wait till Sasuke comes out of the barrell and fights Naruto" that would obviously be a spoiler, because 1) It was going to happen and 2) I imply that it will happen and that I'm just waiting to see it happen. Interestingly, if someone had used the spoiler wording on something that wasn't going to happen they might have been written off as speculative by a mod who had read the manga. The point being that the plot should be a surprise to anyone who only browses the anime forums.