Apps essentially exist because of the limitations of the mobile OS - or, rather, the browser of the mobile OS - to access web content. As the web is changing and mobile devices are progressing (from a hardware and software perspective), apps are really becoming redundant unless they are embedded as part of the natural interface. Certain pieces of functionality make sense to keep "app-ified", but others i think will converge to become part of natural interfaces, much like what has happened to twitter with iOS5 and facebook across all mobile OS's.