"My (and your) 10k, 100k, 200k line C# applications are not writable in JS."
I don't know that this will be true for very much longer, if it's not already been disproven. Javascript isn't the greatest language out there but it's gain functionality that is removing the limitations that uses to plague it compared to other languages. Slow VM is not longer true, no multithreading is not longer true. Webworkes are a little odd for sure, but they still make it possible to build multithreaded applications. WebGL/Canvas allow for some very advanced graphical applications. You can now access local storage, a database (and in node, other databases), new ArrayBuffers and such. It's a different environment now.
I can't point to any (GMail client side code must be pretty big), but I do have a 5K one that I work on daily and it's not a mess. This project is still very much in development and will grow with time.
It's not 50k and it's for sure not a project with 20 devs but even this size was unthinkable earlier.
I'm working on a backend in node to take advantage of Websockets.
I can't show you one either. But I can tell you that JavaScript, done right (which is a big caveat), is a great language. People think it's a toy because of its history (and a good number of embarrassing mistakes in its design), but it's very expressive. It has borrowed many of its core concepts from Scheme.
I think he's talking about the maintainability of such an app in the hands of your average joe programmer, not the sophistication of the language. Also, static typing does have it's advantages, particularly in that it's easier to write tools for developing and debugging those languages.
It's not just Gmail and Node. It's Live Mail and Yahoo Mail and dozens of other Web mail apps that now dwarf desktop mail systems -- at least with consumers.
It's Microsoft's Office Web. It's Google Docs. It's Zoho Apps. Yeah, there are hundreds of millions of users there already.
It's YouTube and Facebook and Twitter.
These are applications with logic and complicated functionality and they're built with HTML and JS and they have hundreds of millions of users, each one of them.
If you think that the Web is "niche" you're in for a rude awakening over the next few years.
"My (and your) 10k, 100k, 200k line C# applications are not writable in JS."
Actually, they are, and quite well. But not by the developers that Microsoft targets. Those developers need a lot of hand-holding to get used to async programming, prototypal inheritance, closures for encapsulation, etc.
So actually, I'm agreeing with you -- there's no way that's where Microsoft is heading. They'd be more like to drop all their programming languages and tell everyone to switch to Lisp.
You don't build applications with logic and complicated function out of HTML and JS. Not today, not tomorrow.
My (and your) 10k, 100k, 200k line C# applications are not writable in JS.
Sure, there is GMail and Node.JS as examples. But thats kind of a niche compared to everything else.
HTML and JS are just going to be another way do to UI, and nothing else. You'll still need to write the C# app and use .NET to do the backend.
HTML/JS will be another option right along with XAML/WPF and SilverLight.