There are already 'planes without pilots. Care to have a look at the loss statistics for military drones? Put simply, there is a hell of a long way to go before such technology is implemented in commercial aviation. It is very much disputable that there will be airliners withouts pilots within 20 years. In fact, I'd say it's almost a nailed on certainty that there won't be.
There are reasons for this though. Modern UAVs by and large are single engine and are not certified with the levels of redundancy exhibited by transport category aircraft. UAVs don't bother with systems such as anti-icing and de-icing and by and large still have a human operator to land them (Predator is landed on site and is not autoland) and its for these reasons the loss rate is higher.
Do I see completely autonomous transport cat aircraft in the mid-term? No. I can imagine a single pilot operator though, sat in first, on some pretty hideous crew duty days who can step in if there is multiple system failure. We wont see the step straight over to no pilots, but there will be an intermediate step whilst the concept is proven and issues shaken out imho.