Zuck's on the phone with (antsy) investors right now, and, of course, the question of the unicorn Facebook Phone came up. His reply? No, The Book isn't building a phone.
"Building out a phone wouldn't make sense for us to do," to be precise. And he's probably right! This, of course, doesn't mean that Facebook can't ask, say, HTC, to build a "Facebook Phone" instead of Facebook building its own Facebook Phone internally. They already tried that once, remember?