Unlike Android and iOS phones, Windows phones until recently was heavily dependent on firmware for OS updates. If you happened to be the owner of Lumia Phones, then this might not have occurred as a big problem for you as Microsoft in the past has always rolled out their OS updates along with the firmware update for their Lumia handsets.
Lumia phones that operated on a Windows 8.1 had a firmware called Windows Denim, while phones that ran on an OS that was higher than Windows 8.1 were known as Windows Cyan. Microsoft has recently announced that there would no requirement for any firmware update for their phones from nowonwards.
This however, does not mean that there would not be any firmware update. It simply means that the firmware update would be independent of the OS update.
Now we are not very sure about what would be the impact of this update on Windows phones, since there has not been any significant news regarding the Windows platform in the recently held Mobile World Conference. However, one thing is quite clear that this move would quicken the release of Windows 10 handsets from other manufacturers.