opps

can this "ken" be applied to the future tense? e.g. "Kompartımana dönecekken, koridorun sonundaki vagon kapısı açıldı;" 

I cannot comment on your example, but one of my books says that you can use it following future tense suffixes.

If you ask "can -ken be added to -cek", the answer is "yes". 

cek + ken combination is possible..

yiyecekken, iyileşecekken, oturacakken, etc

It is combined gerund.. and used as adverb of time and adverb of manner..

The main verb (predicate ) is always past (as in your and henry´s examples )

Let´s see it in a joke:

paddy x man, paddy y man and paddy z man find a wishing slide one day. paddy x man goes to the top and says "Gold!" and slides down and lands in a pile of gold. 

paddy y man went up next and says "million pounds!" and slides down and lands in a million punds!

paddy z goes up and when he was just about to sit and slide (=tam oturup kayacakken) he slipped and went flying down yelling "Sh**!" 

***

If you ask, "can -ken be applied to the future tense", the answer is again "yes".

The combination for future tense is er+ken..

giderken görürsün, alırken bakarsın, kullanırken farkeder..

or

giderken göreceksin, alırken bakacaksın, kullanırken farkedecek.. 

***

er+ken can be used with all tenses:

alırken görmüş

incelerken farketti

dururken biniyor

giderken ağlayacak

severken aldatmıştı

okurken ağlar

etc.