[morzh]

Ron

Indeed if the transistor output oscillates it will try in no time (subsecond). Had it happened to me.
This said, most output amps, even those with one supply are designed as DC amps with DC blocking caps at input and output if one supply and none with dual supply (and differential amp for the input stage). They are also frequency-compensated to be stable and this in a well-defined amp does not depend on whether the load is there or not.

A not so well designed amp might go into excitation but .....bad designs are bad designs, this is it.

Here's a food for thought: many if not all transistor amps have the button that disconnect the speakers. Do you think they would do this if the amp were to oscillate?
My Kenwood has it, and once on a while they get disconnected, and I see that bar moving with no sound, and then I know the speakers are not on.

So....no, a good amp will never oscillate with no load.