Yes, I agree that this scenario is possible. Just a what if scenario here, but if a hurricane comes along and spreads this crude and toxic dispersant all over everything, or if that dispersant does become gaseous and is rained out over land, I am leaving right away, I will not wait to be evacuated. I am already of the opinion that we are looking at a major event here.
The dispersant is essentially glorified detergent and biodegrades over a matter of weeks. No more chance of it becoming gaseous than the box of detergent in your laundry room.
As for a hurricane, they have little effect deeper than a few hundred feet. It would probably help biodegrade the oil nearer the surface by oxygenating the water.