The basis for the speculation? The invite prominently displays Facebook's inbox logo. With some additional features, Facebook may even compete with your current e-mail provider, the theory goes.
Facebook hasn't confirmed the speculation, of course, and there are alternative explanations for what the social networking site may unveil. (One possibility: Facebook could bring its chat product to mobile devices.)
But let's imagine that Facebook's long-rumored overhaul of its Messages product does transpire, either at this event or in the future: Could it pose a threat to existing e-mail providers? Will Facebook users begin to use Facebook Messages more, and their existing e-mail accounts less?
While I'm usually bullish on Facebook's ability to make any new product stick -- with 500 million users, even a minuscule adoption rate means millions of users -- I'm not sure the company would be able to dominate e-mail completely.
In one context -- personal communications -- Facebook could certainly make inroads. The service is already the leading venue to connect with friends online, and providing standard e-mail features such as POP, IMAP, attachments, forwarding and an "@facebook.com" e-mail address would possibly lead some users to retire their accounts on Yahoo, Windows Live Hotmail, AOL or Gmail.
For Facebook, this would be a masterstroke: Virtually all of its major competitors have popular e-mail products. What's more, by combining social networking, chat and e-mail, Facebook would become the hub of online communication.
However, there's very little chance that Facebook Messages will ever be used for professional correspondence. Facebook is already banned in many corporate settings: It's considered a time-waster and a potential security threat to some companies.
Even for those unburdened by such restrictions, it's hard to imagine anyone conducting serious business through Facebook accounts. For instance: Would a job applicant appear more professional sending his or her resume via a Gmail address or a Facebook one?
It's clear that Facebook wants to become the ultimate contact list for everyone on the Web: Its social graph is an attempt to map all of the connections between its users.
And yet the name "Facebook" is still strongly associated with personal pursuits, from photo sharing to playing FarmVille. To shake off those associations would be an arduous task.
Facebook could, if it so desired, become a leader in personal e-mail between friends and family members -- but for more serious correspondence, it's unlikely to be the medium of choice.