There was always rumors of romancing Yosuke and it makes a ton of sense. He fawns over the protagonist, he's very homophobic, and it was very obvious from behavior that Yosuke was somewhat bi-curious.
Initially some attributed it to Atlus wanting to go the other way with the sidekick character where instead of him being insanely jealous of you like Junpei was in Persona 3, he instead is actually drooling over how cool you are mentioning it to you and everyone who meets you, including confiding in you as we see with Yosuke in Persona 4.
http://i.imgur.com/0UFI0T9.jpg