"Written text" can mean one of three things: (1) handwritten words on a physical piece of paper; (2) mechanically printed material on physical paper; and (3) written language either on physical paper or in an electronic medium. In all three cases, it's unlikely that written text will be around beyond the next fifty years, simply because people are hardwired to prefer oral and visual communication, and such communication conveys things better. The written word was always an intermediary between a source of communication and the oral and visual receipt of such communication, and, with the advent of ever-easier communication that is already oral and visual, the intermediary is bound to disappear.
The written word has two major disadvantages to oral and visual communication: First, it encodes information in a way that requires learning. While it doesn't take any special training to demonstrate something, point it out, or describe it in words, it takes years to learn to write and read. Second, and more importantly, writing involves translating sensory input, spoken words and thoughts into a medium that represents them at best imperfectly. People naturally resist the imperfection and learning curve involved in writing, and it takes both carrot and stick to get children to learn to write and read. Many adults remain poor readers and writers their entire lives. If it becomes possible to communicate with spoken words and images in any situation, no one will bother learning to write and read or to use writing.
Such a change is already happening. Right now, most cellphones can record video that includes images of what they are trying to describe, as well as their own spoken commentary about it, and that video can be transmitted thirty thousand miles around the world. Sending a written text message, meanwhile, requires thumb contortions. Even now people prefer to communicate orally and visually whenever the written word can be avoided. Within the next half century, as communication technology continues to improve, writing will disappear from disuse.
Handwriting is already disappearing in developed countries. Most children in developed countries learn to type before they learn to write by hand. Very few jobs and very few personal communication still require handwriting. The printed matter industries are hanging in there because of social inertia, but they are also disappearing, with newspapers going broke or online every month. It will take longer for the natural form of human communication, which is words and images, to replace the written word completely; such change always takes longer than futurists predict. But it's a certainty that, eventually, the change will happen, and the era of the written word will be over.