The article's final sentence mentions the concept of Marineland transforming into what amounts to a palliative care or geriatric facility, perhaps run by the government or a nonprofit, which is a perfectly fine compromise to me. What that should entail is swift removal of any young belugas to facilities more able to care for them at that age and not explicitly devoted to breeding or shows, i.e. Georgia, Mystic, etc. It also certainly could entail the sanctuary off Nova Scotia eventually being completed and providing a better long-term home for these or other whales, an outcome more or less independent of all others. All of this would result in the Marineland tank (which honestly looks fairly passable to me, but certainly not 30 whales-passable) being used for a smaller population and giving all of them more space.
I think that should satisfy all parties involved, but unfortunately politically there are rarely such good compromises.