Visual Studio Code would be the editor, Omnisharp the Intellisense platform, I think they were also developing some sort of common debugging interface, etc.
It would be a lot nicer than the current Visual Studio setup, where the installation drags in 6GB of cruft.
Of course, this would involve an internal power struggle between Visual Studio Code and Visual Studio proper, and I hope VS Code wins :)
In the C# talk at Build , they demonstrated visual debugging using VS code. It was pretty awesome.