The technology is certainly available now, and those who believe that human eyes in the cockpit are superior to the optics in modern military aircraft are deluding themselves both in terms of acuity and in terms of all round global field of view when it comes to avoiding other aircraft/CFIT plus of course the ability to use conventional/nvg/flir combined.
The military is developing
autonomous UCAVs which are going to go out, find enemy aircraft and shoot them down. This is orders of magnitude more difficult in terms of other aircraft awareness than merely replicating the TCAS/human eye configuration currently used in manned airliners to avoid hitting each other. Incidentally, I recently saw a brief that showed that in recent TCAS RAs at a large European airline, more than 50% of the RAs were executed incorrectly. A machine would not make those errors.
There are helicopters currently flying in Afghanistan carrying freight which is significantly technically more challenging than airliner automated flight, and those who don't believe there are trains all over the world operating driverless need to spend a little time on google.
RASCAL Blackhawk takes second unmanned flight « Helinews Asia ? Pacific
This helicopter is a whole stage further. Whilst it is still in development, the challenges it is overcoming are a whole step change in terms of technical difficulty compared to airliner operation. It is autonomous. It can find it's own landing spots. You will notice on one of the videos that it is also able to autonomously avoid other aircraft visually.
The difficulty for automated airliners is in no way technical, it is public image, which may or may not be insurmountable.