I think that would be really tough to guess. I heard on the news this morning that this is the largest hurricane in recorded history, and it is moving very slowly...that could cause GREAT damage!! So...who knows....it depends on where it hits, and how long it stays. Also, keep in mind that flood basins in FL are full right now, any effects of the storm could linger much longer. I would postpone as long as I can, or like someone else mentioned, get there early and plan on a "different" type of vacation.
Also, I know you are a pilot....keep in mind that in all likelihood all SWA planes will be evacuated from FL (I flew for them as a FA for eight years...this is pretty SOP for them in such weather), and so,
1) No planes will go in until all runways are cleared and enough jetways are OP to have planes land,
2) Usually, planes are allowed in on a very limited basis after a storm goes in, and
3) Getting planes and crews scheduled back into airports is a real nightmare (esp. after they have ferryed planes to other places (usually BHM or BNA when MCO was down) when their ferrying ran them over duty regs, and depending on when it hits...getting them out could leave them with illegal crew rest, but that's only a concern if it really does "miss" MCO.
Anyway...just my 2 cents based on past incidents...I have spent more than a little "unscheduled" time in BHM or BNA due to weather. Depending on you and your family...I might really try to get there early if it looks like WDW will be on the "fringes" of the storm
Beca