Many zoos and aquariums have animals that can’t be rehabilitated and released. For instance, the Vancouver Aquarium has mostly blind seals because they couldn’t make it on their own. Having them at the aquarium also allows those seals to raise young foundlings so they can be released later. It also generates awareness of the amazing work that the Marine Mammal Rescue does to help so many aquatic mammals that have been hurt by humans.
You can't release the marine mammals, the best we can hope for is a sanctuary that someone can fly them to. Let's hope Steve-o and other celebrities who hated marineland come through with helping to get it done.
You can’t sell animals like these. My guess is that the ones that can be released will be, and the ones who wouldn’t make it in the wild will be donated to other aquariums, so they can get the ongoing care they need.