I take it you think Cullen will still be a templar? If that's the case, which templar faction do you think he will belong to, given the schism between Justina and Lambert?
Justina's. I think his character arc, if continued, will bring him full circle (no pun intended) from moderate to extreme hard liner and back to moderate, both older and wiser for his experiences.
When you think about it, few Templars have the breadth of experience regarding both sides of the Mage/Templar divide as he has. He's been tortured to near insanity by rogue Mages, and witnessed firsthand the corruption and abuse possible in the Templars themselves, up to and including having to take up arms against an insane Knight-Commander.
Of the possible 20 Annulments in the entire history of the Circle, he can have been present for two, or two near misses, depending. He was strident about calling for one, yet preached leniency in another.
Can anyone suggest a better candidate that we know of for a character who could be a true Moderate and yet still be a Templar?
And as Justina seems to be moderate herself, I would expect him to have the potential to have risen rather far if she extends her patronage.