I'd say PLEASE don't take a chance... Look at last years standard paper II and they specified extracts - so you are safe knowing them all.I know they can ask on a specific speech, but I really doubt it. How many are YOU doing to study? Might do 3 max.
Tell that to the kids who sat the 2002 HSC.Wouldn't asking for a specific speech completely undermine the process? I mean surely that would allow a lot of the differentiation to be based on luck rather than proficiency at english.