1) Dart VM runs on the command line and server. You can access files, directories, sockets, HTTP, Web sockets, SSL, and more. So the core functionality is all there, out of the box.
2) When people say "node.js", they usually mean at least two different things. Forgive me if I'm assuming too much, but I'll try to answer. Node.js is "javascript + v8 + server", and the equivalent for Dart is "dart + dart vm + server". So we've delivered that. Sometimes, when people say "node.js", they mean "express + v8", and Dart has "shelf + dart vm". You can check out the shelf package here: https://pub.dartlang.org/packages/shelf
3) There are a few emerging server-side frameworks out there (I mentioned shelf above). Dart VM is asynchronous, so you'll get a Node-esque experience. There aren't plans to make a fully sync server API.
4) That would be cool!