Microsoft has announced at Build 2015 that their new tools will allow developers to compile the Objective-C code for their iOS apps to work on Windows 10.
The new toolkit in Visual Studio will allow devs to build Windows Store-ready apps from Objective-C code used for iOS and OS X, and will support touch controls as well as keyboard and mouse. The tools also allow for integration for Xbox Live, as well as other Microsoft services and features. This technology is already be demoed with Candy Crush for Windows Phone.
No word on whether this will eventually include code originally written in Apple's new Swift language, but it stands to reason that Microsoft will eventually bring the ability to re-compile that code to Visual Studio as well.