It was a mistake from the film makers, not Stephenie Meyer herself, though - but I guess she could have corrected it if she'd thought of it, I think she was involved enough in the films for that. I don't think this happened in the book, or at least I can't remember it that way. And I think they'd have ignored the rule for dramatic purposes even if they'd realised.

I believe it was in the book where Alice shows Aro his future,so no,it wasn't a mistake on either Stephenie's or the film makers parts.

How do you explain her seeing the wolves' involvement, then? Or her seeing the effects of decisions made during the battle, when people changing their minds is another established weakness of her power?

Although it was a plot-hole, not many people picked up on it. Also, that scene was basically the climax of the movie and without it the movie would have kind of let up to nothing? I don't think it was a mistake.

Maybe mistake isn't the word. Error? Plothole, as you said? I don't know how you'd get around it though, unless you thought ahead enough to omit every earlier mention of Alice not foreseeing the wolves.