Microsoft launched the Preview on Thursday, but only to six phones, and certainly not the phones we expected. These Lumia phones can run the Preview: 630, 635, 636, 638, 730, and the 830.
If you had believed tech blogs and tech news sites, you were likely expecting to see Windows 10 Preview launch on the HTC One M8, the Lumia 1520, Icon, 930, 1020, and perhaps the 520 as well. These devices will get the Preview, just not right away.
Microsoft attributed this decision to how carriers had sized OS partitions on devices. Evidently, the carriers pay less mind to how much space is left to users if the devices are low end and midrange, while making sure to maximize available space on the flagships. Here is the official word from Microsoft on this.
“Some context on why we chose these and not higher end phones like the 930/Icon or 1520: We have a feature that will be coming soon called “partition stitching” which will allow us to adjust the OS partition dynamically to create room for the install process to be able to update the OS in-place. Until this comes in, we needed devices which were configured by mobile operators with sufficiently sized OS partitions to allow the in-place upgrade, and many of the bigger phones have very tight OS partitions.
Note that this doesn’t mean that Windows 10 will take more disk space than Windows Phone 8.1, it’s just a function of the upgrade process at this point. Once the partition stitching feature is completed, many more devices will be supported.“
So, in the end, it is a mixture of carrier optimization and feverish speculation by people who usually pride themselves on their accuracy which lead us to a great disappointment when the list of debut devices was announced. Microsoft was very explicit when saying that the rollout would be very limited at first.
Also, cheaper devices sell in greater numbers than do flagships. Any software maker would prefer to get a broad testing base established in the mainstream, versus a small pool of expensive devices.
I believe we will see flagships added to the Preview in March, although it appears that some unsupported devices may be added via a hack if they sport an SD card.