Most people on Facebook talk about what HAS happened, even if it's just happened on their minds. Their intent is already elsewhere. In your example, that person has mentally scheduled to watch it tonight. If she wanted to watch it earlier, she would be googling it right after posting that to FB.

If FB decides to infer intent from posts right away (when the post's content could be relevant to intent) and adopt a role of 'online assistant' with automatic instant suggestions, that will be creepy and, considering the amount of colorful emotions often present in FB posts, is sure going to cause a few interesting situations. But that's a hugely different product from the Facebook and the ad industry as we know it.