In an interview with Wall Street Journal, ASUS corporate VP of mobile communication products Benson Lin revealed that the company is interested in making Windows Phone smartphones. Lin even said that a Padfone-style device "makes sense for Windows 8", but there's no timeline for a release or even a solid confirmation that ASUS will make Windows Phones.
Lin also says that a Padfone-style device "makes sense for Windows 8", meaning we could be seeing a phone-docking-tablet running Windows in the future. However, the current interoperability between Windows 8 and Windows Phone 8 makes it a challenge to get a Windows Padfone up and running. With the Android model, the phone simply powers an Android tablet interface when docked, but in Microsoft's ecosystem two entirely different operating systems are used for tablets (Windows RT or 8) and phones (Windows Phone 8).