According to GPT's 2013 annual results (just released), it looks as though GPT may be looking to put the Plaza up for sale. This could be a positive, particularly if the council gets involved in the negotiations somehow.
8/3 Update: Andrew has pointed me to an article in the Financial Review from back in 2003 (sadly, behind a paywall), when GPT last tried to sell the plaza. Mirvac, Westfield and (the now defunct) Centro were all reputed to be potential buyers. I wonder how different the centre would have been if either of the first two (particularly Westfield, who said they were keenly interested at the time) had gone through with the purchase.