"Nothing lasts forever", starts John Naughton's recent piece in The Guardian. He puts the current tech empires, like Facebook and Apple, into perspective, and compares them to previously glorious hegemonies like Rome which eventually failed and withered. Now, even that is probably giving these companies too much credit. The parallel to Microsoft is probably more accurate; once the star and darling of the tech industry and press, they are now just another boring mega-corp.
One of the reasons Naughton mentions as why these two companies might see dark clouds ahead is their business models built around "walled gardens". That happens to be in vogue right now, but might show cracks once users find that there are too many restrictions. However, before we see these stars fade, there will have to be alternatives. The Android "alliance" is certainly giving Apple a run for its money, but does still not compete in the "fashion category". Facebook has some smaller competitors, but none of which can single-handedly sway users away. What would really tear their stronghold would be a federated model and protocols to social networking, just as what we take for granted with e-mail. Again, there are a few attempts at this, yet no signs that things will change drastically in the short term.