I will have to say that Cullen will be anything but straight . There is a codex of him, that say from what i remember ,there is a rumor around that say ,back when he was serving in the circle of magi and before he saw it taken by demons ,Cullen ,felt in love with mage there. This mage is known to become a warden and after the hero of ferelden. some says he doesnt speak about it because it was an unrequied love and some because of what happened in this circle after .But what is known ,is thar meredith forbiden anyone who speak about the knight captain and this rumor and will punish them throughfully.
soo my guess know is, if you're able to import you orgin save too, and you were a mage, will it have an impact around his romance with the inquisitor ,some revelations maybe like Karl with Anders in DA2. Have the developers remembered this and gonna dig up this story more. After all, this is very thirlling gossip ! being himself a templar (who's pretty much torn by now) ,this can do a very interesting past and be even more intersting if the inquisitor is a mage too !
now i just can't help but imagine him coming out to my inquisitor like 'i felt in love with a mage once who's now the hero of ferelden' and the answers might be like :
diplomatic: love have no bondaries
funny: i bet you regret letting go of him now
hard: then you're not merciless
and the flirt option :why am suddenly happy the hero is a mage and a man, like me !
and am not trying to think about less pervy replies ~~