Whether or not FB is deliberately blocking Tor now, how out-of-line would it be for them to eventually block it in the future? ... FB already has a policy more-or-less mandating real identities...so for them, this is kind of a non-issue, right?

Those two are not the same. Even if they want to know your name, it doesn't follow that they automatically should get to know where you are (i.e. your IP).