This subject has been done to death so many times now, here on PPRuNe.
It may come as a disappointment to some here but, for the foreseeable future, the pilotless airliner simply isn't going to happen and not only for all the computer capability reasons given but, equally, for the much more mundane reason of security.
Dedicated terrorist organisations will have no problem in raiding and taking over a ground control station, particularly in the more remote parts of the world but, with suicidal tendencies, they will be able to manage it in more civilised places too. Alternatively they simply have to produce a jammer that is more powerful than a remote controlling (relay?) station and disconnect a few aircraft from the controlling system, carnage will soon follow.
One final point, the cost of development and demonstration, to a point of safety where the insurance underwriters will come on board and insure pilotless aircraft, is possibly more expensive than keeping pilots on board. No insurance = no fly.