Pilotless cockpits are not going to happen any time soon. Technology has advanced a lot in recent years, but not enough yet to warrant such a drastic change. This is due to obvious reasons many have listed earlier.
However, robots/computers have already taken over many of our job related tasks and continue to do so. Eventually it will progress to the point where two airmen will no longer be necessary up front. Any one remember when airliners used to have three pilots on every flight deck? That was not that long ago.
Single pilot airline operations is something we as a pilot group will have to fight against very very soon. Definitely within our lifetime.