I have learned DIK is not too sensitive about the time it refers to. Anything but future goes.

What about a sentence like

                 My son will have to set off on the journey right after he comes from school    ?

Somehow it hurts my ear to say okuldan geldikten sonra here because it is in the future.

Yeah it is in the future and you should still use -dik.

,

It is ok to use "dık " when we mention future actions. It doesn´t sound bad. 

For instance ;

Ödevimi bitirdikten sonra duş alacağım.

I will have a shower after I finish my homework.

However, we can drop the actions for some cases like in your example ;

instead of 

okuldan geldikten sonra --> After he comes from school.

we can just say ;

okuldan sonra

Because we know that people will know it is "after comes from school " when we say "okuldan sonra" [after school] 

other smilar cases ;

işten sonra [after work]  = After I leave [finish] work

Namazdan sonra  =  After the prayer. --> After the prayer is over.

Namazı kıldıktan sonra - After I finish performing  the prayer.

Namazdan geldikten sonra - After I come from prayer [Mosque]

So, it just makes your message more detailed, informative but at the same time people might find it unnecessary info cus the context already gives us that information.