This is pure wild speculation: I can imagine writing becoming obsolete within maybe 200 years. My logic is thus:
Writing as a technology has only been with us for a small time (6000 years or so, compared to the 100,000 years or so of homo sapien evolution (ohhh, let's not get into how to date homo sapiens)), and it has only been utilized by a large number of people for an even smaller time (maybe 200 years or so, before that most people were illiterate (probably still are)). Hence, writing is an unnecessary and cumbersome luxury we can happily live without should something better come along.
Now imagine that the computational linguists finally get off their lazy arses and give me a computer I can frikkin talk to and can talk back to me*. If I can talk to my computer like a human being, poof goes the keyboard, right? I give a 90% chance of having this as a viable alternative within 50 years**.
Once I'm unburdened of the clunky inefficiency of a keyboard, and once I can preserve and share ideas without a writing system (think bloggingheads), why oh why would I bother with the ridiculous tedium of representing my words in an altogether unnecessary form?
But, you say, writing provides the best way to preserve and share ideas*** because it lets us organize and review and get all meta. No. It does none of those things. We do that. We're just stuck with this third party representation in which to do those things.
But how would academics write papers and get tenure? Good question. First, tenure will die long before writing systems (I give it maybe 75 years). Second, imagine that instead of writing a paper, I can create a virtual me, encode it with a set of arguments about a topic then instead of reading my paper, you engage in a Socratic give-and-take with this virtual me on the topic. Call it iSocrates****
Thus endeth the prophesy.
*I want everything Kirk had. I got the cell phone. The Terrapins are working on a transporter, now give me a frikkin computer I can talk to!
**I just made those numbers up. People seem to like fake numbers, so okay, there you are.
***You didn't really say that. I made that up. This is what's known as a straw man argument. It makes this kind of bullshitting easier.
****Dear gawd that's a horrible name. Let's hope this whole iXXX trend goes the way of eXXX, eXtreme, XXXtech, XXXsoft, etc.