It's cute, although fanfics seem to portray the characters as closer than they are in S4-S5.
Dean/Castiel would work pretty damn well, but there's still the problem of actually bringing the two characters together.
Oh, and it will never be canon. YOU SHUT YOUR WHORE MOUTH
No, but really, don't be like that. You don't go to children's houses on Christmas shouting that Santa isn't real, do you?
How do we know that Dean is bisexualEdit
In 4x14, the siren didn't take the form of a woman to "seduce" Dean; he took the form of a man that Dean could be an older brother to. Which is creepy.