What the few old farts who still know what a RSS feed is, or who pay attention to updates longer than 140 characters, will do when Reader bites the dust, is an open question. Reader wasn't the first RSS aggregator, though it was one of the most popular ones, both for its web-based interface and the fact that it could synchronise with offline reading apps like Reeder, whose authors have promised that it will survive Reader's death.
In my opinion, whatever replaces Google Reader will have to have a more sustainable business model than being provided for free by the benevolent space beings in Mountain View, driven by their ineffable alien altruisms to serve Man. Something with a freemium or subscription-based model, where the users of the service pay an annual subscription which funds its costs, and ensures that it remains viable and its interests are aligned with its users, not other parties, would meet these criteria. Such services already exist; examples include the photo-sharing site Flickr, the Pinboard bookmarking service (which replaced del.icio.us, a free service whose owners decided that Man wasn't cooked quite to their taste), the SoundCloud audio sharing service and App.net, a shiny new ghost town which, on the surface, appears like a pristine, empty Twitter without the sponsored tweets and creeping ad-squeeze.
Actually, app.net may serve as the basis of such a system; while it seems on the surface like a slightly late-to-the-party microblogging site, it is actually a social API, which implements Twitter-like messages, and also gives each subscriber 10Gb of storage; developers are encouraged to build new applications on top of this API. An application that stores a list of RSS feeds, keeps track of new, read, unread and bookmarked messages from them, and communicates both via a web page and an API for Reeder-like clients, whilst hooking into app.net's messaging and publishing features, may well be the killer application needed to provide app.net with a raison d'etre in a world where Twitter already has been done.
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