Newspaper stories out of the area suggest The Blackstone is up but not severely so. It takes a lot of water to come up over the tower bases by The John Street Bridge. Even then, Disney could keep it on the air IF they strung out a longwire and used the (is it still there?) RCA killowatt backup transmitter. It has proven, in the past, to tolerate some really nasty loading under emergency conditions. I rather doubt the newer transmitter would deal with it.
Good question is whether, the site being unmanned these days, whether the Onan generator is still in the basement and whether anybody might care enough to sandbag the door and run a pump or two to keep it from being submerged.
My guess is that, if it's off the air, nobody will care enough to do anything about it until the water goes down.