It seems like Windows Mobile 6.5.3 is going to drop before the major version 7 release, which is scheduled for late 2010. In Windows Mobile 6.5 API documentation at MSDN (Microsoft Developers Network), WMExperts have found out references been made to Windows Mobile 6.5.3, which indicates a new minor version release over the current version 6.5. The said references can be found in “Developing Widgets” section of Windows Mobile 6.5 documentation.
A widget can have a menu and it can also define the action of the device soft keys. These tasks are performed through the Menu object. Beginning with the Windows Mobile 6.5.3 release, touchable tiles replace soft keys. For developers, the change from soft keys to touchable tiles is automatic starting with Windows Mobile 6.5.3. All of the following applies to touchable tiles and to soft keys.
Apparently, 6.5.3 is the same version that we have seen many times through leaked builds from XDA. With International CES 2010 tradeshow scheduled for next week, and MWC 2010 (Mobile World Congress) to follow it in February, there is a chance that Microsoft will announce the availability of 6.5.3 as early as next week. This could very well be the OS that will be shipped with Windows phones in the first half of 2010, or until Windows Mobile 7 is ready for primetime.