That probably won't happen unless either he had his FB password written down somewhere in his will (if any), or if FB gives access to accounts of the deceased to relatives - which, I can imagine, would be a big hassle for FB.
It wouldn't be a bad idea to take up instructions for one's online life in one's will; Facebook accounts to make announcements on and close, domain names to transfer or disband, projects to close / reassign, online contacts to inform, etc.
I should get to that actually. If I died, nobody of the close friends I have online would have any way of knowing, and the RL people I know (few as they are) don't know them either.