Files will never go away. It all depends on the abstraction level that you view the term 'file'. Humans are files, a self contained unit of information (with built in copy semantics!) they have meta data (hair color, eye color, height, age etc). My point is that there will always be a container object of a sequence of bytes of data. Whether that's an mp3 file or a hummingbird, they are still files.

A more meaningful question might be to challenge the notion of a hierarchical file system. The web has managed fine without one, so possibly search across a flat collection is a better metaphor. There are numerous others.

There are, however, interesting possibilities that make files less conspicuous, apple are experimenting with this, where there are pipes between apps, I open a photo, send it to snapseed, pipe it on to tumblr. At no point am I confronted with a file save dialog. Obviously it's a file under the covers, but that's just an abstraction. Files themselves are abstractions. There's really no such thing as an mp3 file, it's just a sequence of bytes we can interpret as one.