DBs are trained to do that. They watch formations and the QB and they can make an educated guess that if the offense does A, they have to do B. If he saw Wilson staring straight at the receiver, he probably had a pretty good idea he was throwing to that receiver. Now, perhaps they gained access to Seattle's plays and one of those plays was that one. But Occam's Razor says that the Patriots DB made a good play on a bonehead call by SEA. So you're going to have to do a little better to make your point.
Lombardi used to say that he didn't care if the other team knew his plays - especially the famous Green Bay Sweep - because even if they knew what was coming, they still had to stop it.