Generators are selling at a brisk pace, but most people do not have one. When power is lost for more then 24 hours a generator loses its effectiveness as its difficult to keep enough fuel on hand to keep it going.
The other problem is if you have the generator outside during a hurricane it can be damaged or blown over and cause a fire. If you have it inside and run it you can poison everyone in the house with Carbon Monoxide. Quite a few people (over 100 in Orlando) were hospitalized for this during Charley.
PS: It almost surely will be a category 5 by the time it gets here as it will be moving slowly over warmer waters soon which will stregthen it. Also there are no other weather systems in the area that will shear it. This is ideal conditions for a hurricane and I expect we will be looking at 165+ mph sustained winds at impact.