"More than any other single invention, writing has transformed human consciousness." -- Walter Ong, Orality and Literacy
It's possible that online writing will actually surpass that of the printed word. The only thing that is necessary to make this so are:
a) quality writing
b) a sufficient shift in the perception of that which is written online
In certain groups of people on this planet, this may already be true. Svbtle is a great example of this, but so too Longreads, a curated set of long-form magazine-style articles that cut across a wide swath of media, both personal blogs and the long-form stalwarts of the existing publishing superstructure.
Indeed, when browsing these new forms of media, I find that they are even more compelling and relavant to than a typical flip through any given magazine or book down at my local bookstore. It's instant, more interesting, much more curated, highly accessible -- anything that has this many things going for it can be considered an inevitable winner.
To earn the audience of thousands of people once took a lucky break (guess who I met at the lunch counter today), the right connection (often nepotistic), or once in a long while, an editor taking a curious look at the latest submissions pile. (Incidentally, even this is changing, with recent YC company Submittable). Today, an audience can be built consistently from the comfort of your own home.
You supply the insight. It turns out, that's the hard part.
What will you write?