I think it will go from two pilots to one pilot and then to zero pilots. When it goes to one pilot, that pilot will be simply supervising the automation, perhaps only intervening under unusual circumstances. I don't think I'll see zero pilots in my lifetime. I think the technology exists (theoretically) for zero pilots, but I think there will be a steep learning curve along with the requirement (of time and money) to "retool" aviation infrastructure.
As far as the steep learning curve goes, I think there would be an increase in hull losses compared to what we have now if we went straight from two pilots to zero pilots as we figured out this whole pilot-less airliner thing. I think the public would be perfectly happy to fly on a zero-pilot aircraft initially, especially when they get to save $1 on their ticket. However, I think after a hull loss or two due to the "zero pilot learning curve," most would be scared off. That's why the airline industry has to get the zero pilot airliner 100% right from the get-go. I don't think they'll get it 100% right jumping from two pilots to zero- again at least not in my lifetime.