This is not the first time we have heard this, but looks like Microsoft is little aggressive here. Throughout Windows Phone 8 / 8.1 update, when it came to carriers, Microsoft was pretty much stuck with them. Denim Update for AT & T 1020 is a classic example of it.
Now if you did read between the lines of Windows 10 versions, It included Windows 10 Mobile Enterprise, where Microsoft made it clear that update will be available instantly than delayed. This means, even if you are using an AT & T Lumia device, you will get the update like you had got for your Windows Desktop.
The same thing is being pointed by ZDNet’s Ed Bott, who wrote:
“If your phone is running Windows 10 Mobile, Microsoft says, it will get all updates, with Microsoft making the final call on when to push the update button.”
“That doesn’t mean the carriers are completely out of the loop. The Windows Insider program will continue after the launch of Windows 10 Mobile, which means anyone who registers with the Insider program can get early access to updates with new features. The carriers will be part of that testing program, I’m told, probably getting access to builds at the same time as Microsoft’s Elite Dogfood group and their input will help Microsoft decide when an update is ready to go out to all devices.”
“But those updates will be delivered simultaneously, to all devices on all carriers, meaning much less opportunity for fragmentation.”
However, there is one last thing carries still have control–upgrading to Windows 10 Mobile–which either way you need to wait. The only way out of this is Insiders Preview, but then some carrier specific things including warranty gets void.