But if you want to do the Windows 8 app there are other ways of course. Cordova has some base libraries that you may be able to retrofit into Icenium. I haven't tried it yet. Or you could just look at the Windows 8 development guides. MS has their own calls to their own WinJS libraries so something like Icenium for a Windows 8 RT or app project isn't really needed. Just use Visual Studio for the Windows 8 apps.
Though I am happy to see Windows Phone 8 apps coming to Icenium for the build once deploy multiple.
Windows Phone 8 apps can be turned into Windows 8 tablet apps with just a few lines of code.
And it looks like there is news that Microsoft will be combining Windows Phone 8 and Windows 8 apps into one store.