While I would miss this place, I can certainly see your reasoning and I can't disagree with it. I've noticed a lot of one-time posters have moved onto to more ... active fora.
It's also been ages since I've messed with Facebook, so if this place shut down perhaps it'd be time to move to ... 2010 or something and search around on FB for information.
I think the biggest thing I'd really miss about this place is getting better-than-average informed opinions on things like star system construction and exoplanet information. For information on star systems, star behavior, and exoplanet for hard (or firm) sci-fi ... this board can't be beat. If I post questions like that anywhere else I'll get a bunch of responses that have nothing to do with science or a deafening silence except for some response by the board's resident guy who has to respond to everything even if the reply is totally unhelpful or thread hijacking.
Everything else, I admit I mostly go to other, more active boards.
Are you thinking of setting up perhaps some alternative venue on some other media, like Facebook?