Yeah, at this point why would they IPO (except to get rich[er], of course)? Obviously they could grow in some unforeseen way, but if they don't have an ace up their sleeve, what business reason would they have for needing additional capital?
Well, there may or may not be a pressing business need for capital, but I'm sure a lot of the current shareholders would see an IPO as a good exit.
I suppose it's possible that facebook could still be acquired, but given how large they are, and the huge amount of cash/stock it would require to buy them, that seems unlikely to me.
