Microsoft has already admitted that the Surface RT won't be upgraded to Windows 10 and it has now said that not all of its Lumia smartphones will either - Despite saying the new OS has been designed to run well on 'today's' Lumia phones. Find out: How to get Windows 10 now.
"Our goal is for the majority of the Lumia phones running Windows Phone 8 and 8.1 to join the Windows ecosystem along with an expected hundreds of millions of PCs, tablets and other devices running the next generation of Windows," said the firm on Lumia Conversations blog (formally Nokia Converstations).
In the blog post it confirmed an update will be definitely available for the Lumia 435, Lumia 735 and the gold-edition Lumia 930. Microsoft gave live demonstrations of features at the launch event on a Lumia 1520.
The news may be a shock for some as the firm tweeted in November last year promising upgraded for all. "We plan to upgrade all Windows Phone 8 devices to Windows 10 in the future :)," it said via the Lumia Twitter account. See also: Windows 10 screenshots.
"Like any upgrade to a new platform, not every phone will upgrade or support all possible Windows 10 features, and certain features and experiences will require more advanced future hardware," added Microsoft.
So it remains unclear which devices (beyond the three named above) will get upgraded to Windows 10. The above statement suggests that budget devices are less likely to be included while more premium Lumias should be able to handle the new firmware.