Other airfields like Parafield and Caboolture also have vacant perimeters that would be suitable, just takes a bit of persuasion and political savvy.
The city GA airports are too interested in developing shopping malls and industrial estates to bother about on-site airpark residential use. They would quietly hope that GA would disappear of the face of the earth and convert what's not been resumed to residential, in which case they would make 10-20 times what they invested.
As far as Parafield is concerned, a huge tract of land in the triangle of Rwy 03 and 08 has been rezoned as Commercial/Industrial that on current valuations would, on land sales alone, net the owners 30-40M after subdivision costs. This all came about following the resumption of land at the S boundary for the new road.
It's also rumored that Lindsay Fox made a killing out of the land acquired for the Freeway upgrade, and anyone who's been to YMEN lately will see just how much the landside development has accelerated, and none of it is airpark.