This is going to come across bluntly, but NO WAY should this site be turned into a PARK...Brisbane CBD and the inner city already has enough parklands and public spaces; Reddacliff Place, King George Square, Queen Street Mall, ANZAC Square, Post Office Square, King Edward Park, Wickham Park, City Botanic Gardens, Roma Street Parklands, Southbank Parklands, Kurilpa Park, the new park at Kangaroo Point and the potential greening of the Howard Smith Wharves.
It is not like Brisbane has this huge CBD that people will struggle to get across, and thus we don't have a limited number of parks/public spaces...
The area could support (as others have said) a theatre/museum/art gallery type set up. I would like to see some sort of a 'theatre district' established in Brisbane, and maybe this is a good spot to get the ball rolling. We could have a couple of small theatres on the site, and maybe down the track the Dendy could be restored to some sort of dignified operation and be an independent/alternate theatre. Brisbane does have a growing arts scene and the city itself lacks theatres (only real sort of theatres are in Fortitude Valley/New Farm and South Bank apart from QUT).
On top of this, it would be good to see a proper indigenous art gallery and/or indigenous museum established to celebrate the culture and history of indigenous people in Queensland. But these might be better off at Howard Smith Wharves.
Hotels, apartments and offices would be built on top of the ground level activities.
A pipedream would be for the Treasury Casino and Hotel to be relocated from their current premises and combined into a purpose built facility at this site. It is big enough to support more restaurants, bars and gaming facilities than it does presently, and the hotel could be much bigger and expansive. The old buildings could be restored and used as (the casino) an elegant shopping centre (ala QVB in Sydney), a museum/art gallery set up or a theatre...
Perhaps more realistic is the creation of a real 'youth driven' precinct with ten pin bowling alley, gaming arcade, flight simulatore, ice skating rink, laser tag, snow park, rock climbing centre, cinema etc etc. Brisbane lacks a popular hang out for teenages and this site's proximity to public transport and large block of land could easily support the above mentioned activites. Offices and apartments/hotel could be built on top
There are certainly many possible uses, let's hope we get a good outcome, eventually