Facebook is holding an invitation-only press event on Wednesday. The brief announcement — that is, the prelude to the actual event — has thrown the social media and blogosphere rumor mills into overdrive. What, the burning question is, will Facebook announce? Much of the speculation has centered around the phone that it is allegedly developing. If not a phone, this school of thought says, then a new, deeper level of integration with mobile devices. Whatever the announcement is, it had better be very significant, said Dan Olds of Gabriel Consulting.