Something I was thinking about.
In the 8/8 Direct, after Sakurai showcased Chrom and Dark Samus, he said, quote: "We have a few more characters to show you before release".
Now, "a few" generally means "three (or more)", at least where I come from. (You'd be surprised how many people don't actually know that)
That's not even getting into him deliberately downplaying the number, of course.
But I would say, with some amount of certainty, that we have more than two characters coming. Of course, we all knew that already, right? ‾\_(ツ)_/‾