I too think its just a matter of time. Aircraft are the most predictable when it comes to type of transport and we already have a lot of automation now a days. However there will always be opposition until a lot is proven and rightly so.
Cars are recently being tried and even though 2 states have allowed these it still takes a lot of time of adopt these. By the these rules trickle down to developing countries it will at least be a good 7 - 10 years. These are just the rules. By the time majority of cars on road are automated it will be a good amount of time .
However I think the airline industry is much more flexible . Even if a new plane will be operating for like 20 years, because its a global industry dominated by few manufactures (at least for commercial) , the adoption scale is global. About 10-15 years from now we could expect something to be made. But by the everyone will be flying in one of those, I won't be living to see it.
Unless of course we don't have any accidents in between that seem to expose an underlying problem . I think the industry is fairly tried and tested but we can't rule out anything , one problem can change everything .
I think trains should be first tried for full automation. They lie somewhere inbetween both in terms of predictability.