Most effort right now with marsupials is more on expanding the small populations that are still present than importing new species. Echidna, wombat and certain wallabies have relatively few holders and are slow-growing populations. Tree kangaroo, bettong, and cassowary have several holders but are still not ubiquitous. Tasmanian devil and koala are especially unique cases. There are zoos looking to get into devil, koala, tree kangaroo and so forth that are waiting for availability. There is also some institutional interest in bilby but my (limited) understanding is Australia wants to expand their internal program and start exports after reaching a certain threshold, and while there is sometimes interest in quoll, their reproductive cycles seem too difficult to replicate without a rather large, multi-institution investment which doesn't look plausible.
In addition, I'd say there's only twenty or so institutions who are committed to Australian wildlife as many, many zoos are content with Bennett's wallaby, red kangaroo, and emu in a yard and calling it a job well done. This isn't strictly a criticism as sometimes there isn't space to work with, although in some cases there are zoos that could do more. I'm proud to say Brookfield is looking into expanding their commitment here, although details seem scarce.
