VS Code does not currently support extensions/plugins. The team has confirmed they're coming at some point[1] but we'll need to see how they set it up to determine the best approach to building an F# plugin for it.
Ionide definitely won't be compatible out the gate, but if the API isn't too different we might be able to reuse some of what we've already done.
The best case scenario would be the if plugin system supports dlls so that we could use the FSharp.Compiler.Service directly[2]
VS Code is using Omnisharp[1] which is build on top of Roslyn so as for now it supports only C# / VB. As far as I know they are working on adding plugin support for it for non-Roslyn language so maybe in the future we will have F# plugin there ( actually, as far as I know, that's MSFT plan for adding F# support in VS Code)
Since VS Code is built not on top of Atom but on top of Electron[2] both projects share just "lower level" possibilities and will both build different abstractions layers on top of it. Unless VS Code team chooses to build very similar API to Atom one direct porting won't be easy.
Ionide definitely won't be compatible out the gate, but if the API isn't too different we might be able to reuse some of what we've already done.
The best case scenario would be the if plugin system supports dlls so that we could use the FSharp.Compiler.Service directly[2]
[1] http://visualstudio.uservoice.com/forums/293070-visual-studi...
[2] http://fsharp.github.io/FSharp.Compiler.Service/