A little bird suggests to The Register that Microsoft's "more secure than others" wireless products will be using Protected Extensible Authentication Protocol (PEAP). He further suggests that PEAP support will ship with Windows XP SP1, and although we hadn't heard that as a possible SP1 addition, Microsoft is a supporter of PEAP, and a while back said a "future version of the Windows client may also include Protected Extensible Authentication Protocol,"
News source: The Reg