A handful of playable monstrous races (all monstrous humanoids, say: gnoll, orc, lizardfolk, goblinoids) is enough to keep me happy. I'm really hopeful that they'll be stated out in the DMG -- it would take 3 pages at most, I figure, since it wouldn't need full descriptions, just the mechanical effects (as in the back of the previous MM). I don't particularly wasn't more or need more than that.
Fingers crossed.