I have not seen anyone predict that Facebook will last forever. I personally wouldn't say that about any company.

I myself predicted that apps would be the demise of fb. I received so many invites that I couldn't keep up - and it was accelerating. But they solved that problem by taking apps off of peoples primary pages. App developers complained and some probably missed showing what kind of ninja they were, but looking at it now, it looks like they made the right decision. I wouldn't be surprised if they manage to fix current problems as well.