During the Computex Taiwan, Microsoft announced an Office Mobile update which will be available for free starting Q3 (which could mean next month already). This update will be compatible with Windows Mobile 5.0 Pocket PC (Phone Edition) devices as well as all Windows Mobile 6 PDAs and Professional and Standard smartphones.
Furthermore, future Windows Mobile 6 devices will have this new version of Office Mobile preinstalled. As expected, the updated Office Mobile version (the name isn't clear yet - some sources say Office Mobile 2006 while others say Office Mobile 2007) will allow Windows Mobile devices to open documents created with the new Office 2007 XML formats.
Documents created using older versions of Office will still be supported by the updated Office Mobile version. Another added feature is support for fax, which means that users who choose to receive their faxes via E-Mail will be able to open these fax documents too (this means most likely TIFF support).
Source:→ unwiredMicrosoft, Announcement, Office Mobile, Updates, Windows Mobile 5.0, Windows Mobile 6.0