Getting new batteries alone is gonna' be expensive, and considering the ride itself doesn't have good bones to it, updating it into something worthwhile would require a major overhaul that would be pretty expensive as well. Which brings up what WAJAS mentions...
A painful example of this is Curse of DarKastle at BGW. All they really needed to do was properly maintain the ride to keep it going, and they didn't. If Seas didn't want to put the money in to maintain that, I just don't see them putting in the money to update Antarctica...heck it's dicey if they're gonna' spend the money for the batteries.
I know folks want darkrides from Seas, but if they can't maintain the good ones they had like DarKastle, or put in disappointments like Antarctica, or dead on arrivals like Submarine Quest, there comes a point where you just have to admit darkrides are just not their thing.