We were there during Matthew last year. Based on our experience, the chances of that happening are pretty slim, not non-existent, but slim. We had nothing to do for about 24 hours of our trip other than sit around and talk to other guests and CMs. Remember, the fact that you are not able to get out because flights are cancelled or the airport is closed, also means that others are not able to get in. We made friends with some people that got stuck there 2 extra nights. They were told there were a lot of cancellations for people not coming in (some who could not get there with flights- and others who cancelled because they did not come with the storm coming) and had no trouble staying-- they were given a discounted rate (I think they asked for a discount- which it never hurts to ask- the most they can say is no). We also met some people who had been evacuated from Fort Wilderness and into resort rooms. I also recall some people that were told they would have rooms, but would probably have to move out of CL, but they wound up being able to stay in CL. I could be wrong, but I think the shelter with cots that someone talked about was for CMs. We talked to CMs that were running lobby activities and playing with kids, as well as some of the other CMs. I know they were all being kept on property. I remember some of them talking about being put in resort rooms. It seems like someone else was talking about an area where they were putting in beds for a whole lot of CMs to stay if necessary. I would not stress about not being able to find a room if you were to get stuck there. Based on our experience last year- that did not seem to be a problem- just look at this board and all the people who have already cancelled or moved their trips. It is never a sure thing that it will not be a problem, but I think there is a much greater chance that they will have a room for you, or will do something to help you. They really did the best they could to take care of the guests last year under the circumstances. What stinks is the extra cost of basically being stuck inside at a resort for another night or two.
You have to do what you think is best for you, but if it were me, I would probably cancel. I think even if the hurricane veers east and skirts by, there is a good chance you are looking at a lot of rain and some wind.