I have the same interest!
I have a game written in C# and XNA for Windows Phone 7+
It looks like that porting the game to C++ using cocos2d-x and Universal Windows Apps is the right way to go in order to move the game forward and also port it into the Windows Store (and maybe on other platforms too).
I tried to clone the WinRT branch of cocos2d-x, migrate it to Win 8.1 but I can't compile because of WINRT_EGL_WINDOW identifier not found. Even if I can compile I would not know exactly what I should do to actually use the framework in universal apps.
Could you please let us know what are the plans and if a template will be available?