imho, sea lions are an iconic 20th Century zoo animal.
London had a single South American fur seal for a period after the Californian sea lions left (for Whipsnade?), around 1991-95. At some point before the fur seal arrived, the sea lion pond was altered, the protruding rocks in the pond were removed, as well as some of the rocks around the edge. In fact, the only rock work left was at the back, I believe this is listed and will be incorporated into the design of the tiger exhibit.
I would be surprised if Edinburgh couldn't find the money to bring the exhibit up to scratch, however I think most zoos would opt for a spectacular new exhibit or to give up the species altogether.
With this species, given there hasn't been a successful birth since perhaps the late 80s, (at Curraghs Wildlife Park, which no longer keeps sea lions), I really feel zoos without sufficient funding should not be attempting to keep Patagonian sea lions. Given the lack of success in breeding at Dudley, the lack of success in rearing pups at Twycross, and the single-sex group at Colchester, perhaps another average set up for this species in the UK is not needed? Far better that Edinburgh plough some of their anticipated panda profits into a 'returning' favorite species, such as the sea lion, giving them a high standard of enclosure after a period of absence....