Let me try to give some useful answers, beyond "most if not all these questions are simply misguided".
- Zero. Tone-deaf marketers have been trying to "reinvent the book" for over a decade now, always in ridiculous ways that had no chance of working even if the idea had anything good about it, and it doesn't. Books are already as close to perfect as any medium can get, after thousands of years of people improving the craft.
- Eleven. It has already happened.
- The question is wrong. That's not what people are missing when it comes to text adventures.
- You mean like virtual tabletops? Or play-by-post? Because people already play together online, they've been doing it as soon as it was possible. It's also not what players of text adventures are looking for. And there's a reason why people want single-player games sometimes. AI Dungeon solves the wrong problem in the wrong way, not to mention how much computing power it uses for minuscule gains.
- Bwahahaha. Again, there are reasons why people like text as a medium. It's not a technical limitation.
- You mean like Twine? Because it has already happened, it's just not pretentious crap hiding behind pretentious jargon anymore.
- That... is exactly what Twine does. Or GrueScript.
- Zero. Aesthetics matter. Text matters. People still go to puppet theater, don't they? It has yet to be replaced with robots, even though we can do it just fine now. Not to mention easy of authoring.
- Zero. Again. aesthetics matter, and visual novels are infinitely easier to author as well. Besides, it's not a zero-sum game.
- No, no, no! Why would that happen? Even if everyone liked VR and could afford it (and VR is inevitably more expensive as any other display tech, all else being equal), why would it replace everything else? Not to mention the inconvenience.
- I seriously doubt visual novels are the most popular form, or at the zenith for that matter. And even if they were, things always change.
Seriously, it doesn't work that way. The future of interactive literature is more authors, more works, more and better tools, libraries of reusable assets, and more importantly a sea change in how we perceive copyright and fan fiction.
Tech is not the future. People are. Focus on the people.