I also tend to think that we are a long way off (probably multiple decades) before we see single/no-pilot 121 ops, if ever. It's not a technical/engineering problem, however. I think the guys that say "it will never happen because it's impossible to do X, or what about how hard it would be to do Y" are missing the mark a bit. Any type of technical challenge or hurdle could be overcome eventually. Sure, it's great to list all of the things that would be hard to do, but they could be done given enough resources.

I think the far more compelling reason is economical vice technical, along the lines of what Rickair was talking about. We can overcome any technical challenge, but we can't overcome any technical challenge for the same or lessor price then an FO can do it for. It's one thing to be able to do it. It's alot harder and much farther off to be able to do it for less money.