Before the Left Behind DLC dropped, I had talked about the ending being quite clear- Joel wasn't just selfishly lying for himself, he was giving Ellie a choice, and I think that simple fact will tie directly into this sequel. Honestly, Naughty Dog will have a lot to live up to, and perhaps they can find a way to balance the intense emotional journey with some of the irritating game mechanics of the first game. A good shiv shouldn't break after 2 damn uses. It's a damned annoying mechanic in every single survival game made.
I also wonder, but very much doubt, if they'll give us a small PS Vita game tie in. Maybe some other stories in the world of The Last of Us, but done in a manner as Uncharted: The Golden Abyss was.
The Last of Us 2 has no release date, and is "still in early development."