In the recent days, Microsoft made several times clear that none of today's Windows Mobile 6.5 smartphones will get a Windows Phone 7 Series update because today's 6.5 smartphones don't support the 7 Series requirements and users have to wonder why Microsoft is so strict? While the exact feature-requirements are yet to be announced, let us have a look at one of the obvious differences between Windows Mobile 6.5 and Windows Phone 7: The buttons and the button layout. As a matter of fact, Microsoft confirmed in Barcelona that Windows Phone 7 Series devices require the Windows, back and search keys as well as a camera key, in addition to the volume rocker and power button.
However, Microsoft isn't supporting call send/end keys but calls will established through the graphical user interface. Furthermore it was confirmed that Microsoft will distribute operating system updates in the future by itself (doesn't matter if these updates are distributed over the air (OTA) or as a download to the PC (side load)).
Now - if we take the HTC HD2 as an example - HTC's hero smartphone might feature all the technical requirements (CPU and CPU speed, camera resolution, compass, etc.) but it's quite obvious that the HD2 sports a different button layout:
Now, it would be pretty easy for HTC to adopt the Windows Phone 7 OS and customize it to work on an HD2, including the support of the call send/end buttons as well giving the Home button a new sense; while the question would stay which button to assign to the search key but anyway - what's next? As soon as a HD2 is updated to Windows Phone 7, it's a device which Microsoft will/have to take care about in future and it means that Microsoft is responsible for future operating system updates. However, since Microsoft is providing updates on the Windows Phone 7 requirements, the question is how Microsoft should deal with the extra buttons (call send/end, home) or missing buttons (search, camera) since these button assignments were part of HTC's previous customization? As a matter of fact, Microsoft wouldn't be able to roll-out OTA updates for the HTC HD2 but HTC has to release another customized HD2 ROM update which would lead the whole unified Windows Phone 7 Series idea ad absurdum!
Therefore, Microsoft's cut makes absolute sense, even if it's hard for today's HD2 owners. But since Microsoft Windows Phone 7 Series should be a future prove restart, Microsoft had to make some strong decisions which includes to deny update possibilities for devices which aren't 100 % Windows Phone 7 compatible.
At the end of the day it's a question how to support Windows Phone 7 Series devices in the future and users often requested and asked for direct OS support from Microsoft. Microsoft might have specified this to the limit but it seems it happened to the benefit of the future platform strategy.
And as Microsoft said - the current lack of supportable devices doesn't mean that none of the upcoming Windows Mobile 6.5 smartphones will also be unable to get a Windows Phone 7 series upgrade but it means that it's quite easy to identify which device might be able to be upgradeable: It has to feature a Windows start, back and search button as well as a camera key, volume rocker and power on/off button; not more but also not less!
Last but not least please note that the thought above represents my view only! It's neither backed-up by any official Microsoft information nor confirmed by Microsoft. It's just a result of a recent research and discussions with fellow industry insiders and mobile device users.
Cheers ~ Arne