Almost moot to even think about, because im certain I wont see a pilotless airliner in my lifetime, and I highly doubt i'll see a single pilot airliner while my heart is still pumping.
1- if we won't let trains, which run on a defined path, be automated without a guy driving it, then we're not going to have something as complex as an aircraft be automated with nobody at the helm.
2- 787, A380, New 747 etc....These aircraft are designed around the 2 flight officer concept, and these aircraft have at least 50 years in them.