Accccctually. Yes, is is a guarantee. As powerful as a cat 5 may seem, it is still obedient to the whims of our atmosphere. It responds and moves within limits just as any other storm, and those limits are dictated by the atmospheric conditions around it. COULD it turn and make landfall? Sure, the rtough is big enough to allow that. WILL it? Well, you have to give it a reason to... an atmospheric reason, or one that is very strong in the water (like a heat knot, which is what they think caused Charley to skew off to the S, but you won't find these in the waters here).
The reason for the debate where and what it was going to do, was that the speed of the system pushing the trough, and the jetsream which shapes it, was all in flux. Now that everything has come together the info is a lot firmer.