[CrownStem]

That could be true, but I believe it to be unlikely in this case.

It's easier to benefit from a false-flag attack by just doing it- denials don't carry as much weight in an emotional, post-attack context. When forewarning is given for a false-flag, you give the accused a chance to back away and say "it's not us" before an event, lodging enough doubt that the size of the crowd with torches and pitchforks isn't as big afterwards... I think this would be counter-productive for the guys staging the false-flag attack.

[CrownStem]

Looking at your idea from a different angle: I guess it could be useful for an opposing group to make the threat, in order to make Anonymous look impotent if it's not carried out, while the opposing group takes credit for "stopping" it.

Who knows... -We- surely don't. I feel like I'm outlining a plot for a Tom Clancy novel.