Does Dietrich Bonhoeffer fit the requirements to be declared an official martyr? I'm wondering what the Roman Catholic church stance is on this man and whether they will ever declare him a martyr? I'm guessing he is too protestant to ever have any recognition in the Catholic church.

What has the stance of the Catholic church been in regards to other Nazi dissidents?
It is dogma that non-Catholics cannot be martyrs:


  …no one, whatever almsgiving he has practiced, even if he has shed blood for the name of Christ, can be saved, unless he has remained in the bosom and unity of the Catholic Church.—Pope Eugene IV, Council of Florence, decree Cantate Domino


(Martyrs, saints, all those in heaven are saved.)