It really didn’t bother me, or make me worry about destiel/deancas AT ALL, and you wanna know why?
Because it’s freaking Metatron–Metatron who, despite studying human stories and literature for hundreds of years, clearly knows nothing about humans on a personal level. Like, he knows humans like we know the life cycles of ants. He generalizes. As the villain, hemonologues.
And he also doesn’t give a shit about Cas at this point, either–if anything, he’s telling Cas to live a normal human life to add to his misery as he steals his grace, not give him advice on what to do with his life. He’s not using this moment as a moral soapbox, and nor is he a thinly-veiled mouthpeice for the writers’ secret heteronormative agenda (I mean what?). He’s throwing out facts of the basic human life cycle to taunt Cas, to remind him of his impending humanity, because he doesn’t know the truth about Cas or care to know. In his eyes he’s throwing Cas to the mangy dogs and mocking him.
I don’t take this line as an omen that a female love interest will pop out of nowhere, because (1) that’s not something the writers would lock themselves down to so early (2) it’s a throwaway line as I’ve just described, and (3) also we’ve seen how well that’s worked in the past //sigh//. Instead I take it as yet more proof that Metatron, despite being the scribe of God who has lived among all the stories and tales of humankind, just doesn’t GET IT. Because clearly, he’s just as prejudiced as Naomi was, but just a different strain of the ignorance of heaven. It will most likely cost him dearly in the end.