Well, that will be very sad for you if you are disappointed. But, one, there's no artistic reason why the series needs to have a happy ending and, two, there is a wider range of possible happy endings than Sam settling down with a girl.

I have no objection to the series ending with Sam in a stable monogamous het relationship if that's what happens, but I find the way you inanely pop up and make variations on this same fucking bland, soppy, oblivious comment every time the subject comes up so goddamn annoying that I hope the series ends with Sam going darkside and volunteering to be vored by Dick in a ritual that brings the universe crashing down. Also a puppy dies. And Dean is tormented by gingivitis for the rest of his lonely, miserable life until he dies in a bizarre golfing accident. Just to spite you.