Cool stuff, version 4 doesn't sound like it will go new ways, but there are some interesting discussions going here. What about tighter integration with client side frameworks between the server side and its (view)model and web services, the connection between js and c#..? What needs to be done to get a 'clean' client side code, how can tooling help there?
Some thing I'm also thinking about are push based web apps, It might be not a common use case, but imagine having like a observable collection server side or something that pushes changes to the web app.
By the way, does anybody of your team use Resharper? If not, how can you live without it?
I would be interested in how Native code could be sandboxed in a safe and platform independent environment. I am thinking about something like Googles Native Client technology, that compiles C++ to one binary, that can then be run in the browser on every OS platform and can only access those libraries provided by its host, in this case, the Chrome browser. Such kind of technology would also solve the problem of public marketplaces for phones and other os, that cannot trust native code(thats why WP7 marketplace is managed code only), so how about sandboxing it? How do you see the future of native on the web and on the phone not only as a engine everything is running on top of, but also as a dev platform for third parties?