An unfortunate inevitability —

No Windows Phone 8 upgrade for current phones

They'll get a smaller 7.8 update instead—including new Start screen at least.

As long suspected, users of the current Windows Phone 7.5 platform won't be able to upgrade to the next major version of Microsoft's smartphone operating system, Windows Phone 8.

Instead, they'll receive an update called Windows Phone 7.8. The only feature that Microsoft has confirmed will be included in the 7.8 update is the new Start screen, with its full-width tiles and greater customization. However, company representatives left open the possibility that other Windows Phone 8 features might be included in the update.

Windows Phone 8 includes a number of features that require appropriate hardware not found in current devices, such as NFC and multicore support. It also has features that are pure software, such as the new multitasking APIs and speech integration. Including these pure software features in the 7.8 update would likely improve the longevity of current phones, as they would be able to use new apps that take advantage of the new capabilities. Nevertheless, Microsoft may not feel it's worth the effort.

Similarly, though the company has only spoken of the new Start screen, Windows Phone 8 might contain other user interface changes. Such changes would be pure software, and hence feasibly incorporated into the 7.8 update. Again, it depends on whether Redmond thinks it's worth porting them to the old platform.

This is bad news for any current users of Windows Phone. Just how bad is less clear.

If 7.8 really does contain nothing more than the new Start screen, the value of any current Windows Phone handset has just been slashed. As soon as Windows Phone 8 hits the market, applications that make use of its new APIs and capabilities will be released, and none of these will run on current phones. While this is fair enough in the case of apps that depend on, for example, NFC—software updates can't change the hardware, after all—it's less satisfactory when it comes to apps such as VoIP. The only thing holding these apps back is software, and that's eminently changeable.

On the other hand, if 7.8 contains all the new APIs that make sense—so excluding NFC (as it requires hardware), and native code (as it requires the Windows 8 core), but including VoIP and turn-by-turn multitasking, the non-NFC portion of Wallet, and any other UI improvements that Microsoft is making—then the situation is much rosier. Current users are still being left behind, but they should continue to be able to get new apps and new capabilities for another few years yet.

Channel Ars Technica