When you host a solid project like CodeMirror on a local Node.js instance, which fortunately has a heavy focus on I/O, you start to get those capabilities back. See something like Lighttable, which is essentially ClojureScript on top of Node.js, but sadly isn't open source (yet?) I think we're still a far cry from it, but maybe that'll be the future of Unix-based text editors, maybe that's what will eventually supersede Emacs (I say that as an avid user.)
That said, I wish I could pin some of my hopes to the upcoming Guilemacs.
As soon as it launches, Light Table will be open source.
"Will it be open source?
I'm a firm believer in open source software and open source technologies. I can guarantee you that Light Table will be built on top of the technologies that are freely available to us today. As such, I believe it only fair that the core of Light Table be open sourced once it is launched. At some level, this is an experiment in how open source and business can mix - it will be educational for us all." - http://www.kickstarter.com/projects/ibdknox/light-table
That said, I wish I could pin some of my hopes to the upcoming Guilemacs.