Between now and then, enterprise users and consumers alike will need to buy new smartphones. Some devices will be able to upgrade from Windows Mobile 6.1 (which is the current version available) to Windows Mobile 6.5, but not all of them will. Since most people buy cell phones with two-year contracts attached, they'll be holding onto those devices until long after WinMo 6.5 -- and 7 -- become available.
From my perspective, there's no longer any motivation for people to adopt WinMo 6.5. True, 6.5 will bring with it a large number of usability improvements, but from what I know of Windows Mobile 7, it will be a complete overhaul and re-realization of the entire mobile operating system. The differences between 6.5 and 7 will be vast. The likelihood that devices running WinMo 6.5 can upgrade to 7 is low.
Without the ability to upgrade between versions, I foresee many people making due with Windows Mobile 6.1, skipping WinMo 6.5 completely, and waiting it out until WinMo 7 appears.
My colleague Ed Hansberry pointed out, "Not only do we know 6.5 is out this year, WinMo 7 will be out within 12 months of that. This is a fast release cycle, as most WinMo upgrades are about 18 months apart at best."
For comparisons' sake, it would be a similar conundrum if Apple were to make Snow Leopard available in June 2009 and then in August 2009 say that the next version of OS X will be available in the first quarter of 2010. Why would anyone bother upgrading to Snow Leopard when we all know that the next OS is right around the corner?
Microsoft now has to work hard at differentiating WinMo 6.5 from 7, and convince people (and its handset manufacturer and network operator partners) that migrating from WinMo 6.1 to 6.5, and from 6.5 to 7, is a viable plan.