Don't get too excited, although I don't personally have authority to dismiss this, I have word that this is a completely FALSE rumor (sorry, I can't back that up-- at least do yourself the favor of being skeptical).

Edit: Confirmed http://twitter.com/Microsoft/status/14850981422 (Microsoft official Twitter)

Quote: "Steve Ballmer not speaking at Apple Dev Conf. Nor appearing on Dancing with the Stars. Nor riding in the Belmont. Just FYI."