I wouldn't and don't expect to see any main/major characters given a relationship with any character on a romantic setting, straight or not. (Cheerilee and Big Macintosh are minor characters) It's something that could get controversial if you go outside of straight relationships (inside straight relations ships would be constricting to character and not relative to kids), and we've already figured out that Hasbro doesn't like to get controversial with this show, or at least any form of offended complaints.
Now here's something that could be scary,
a new toy baby pony named "Princess Skyla"Why scary? Not because the toy looks awful, but because past toys have had impacts with the show itself. (Rainbow Dash's pet tortoise Tank was a toy before it became part of a planned episode) This baby could appear in Season Three, or not.