This is an interesting question because I guess it depends on a lot of other factors that could somehow influence the outcome. Certainly we can say that all those who give Oedipus evidence in his quest for the truth do not do so willingly--Oedipus needs to threaten, cajole and force them to reveal what they know. Therefore if Oedipus had abandoned his quest it is possible that he could have got away with it. However, imagine the scene - Thebes is suffering gravely as ever more people die from the mysterious illness. If Oedipus hadn't found "the truth," then more and more people would have died and perhaps an Oracle could be found who wouldn't be so shy of speaking the truth. My own personal feeling is that this is a case where the "truth will out" whatever happens, and Jocasta, even were she to be successful, would only put of the inevitable revelation that, at least on some level, she herself is aware of.