Just curious - why replace vim or emacs?
It can be strategic even if limited to quick edits and for some subsets of the repository now. Anyway I can think of a GitHub augmented with an IDE and integrated with a CI and CD system with deployment to a Heroku. It could let you write code from pretty everywhere, occasionally even on a tablet or a large phone. Somebody will use it.
i love vim a lot (use evil in emacs), except vimscript. I hope oneday I could use neovim with atom/st2 as frontend.