We can now confirm that the Build 8.15.12492 that we have reported below is in fact Windows 10 for Phones‘ latest build under internal testing. We have also reported sighting of Windows 10 for Phone build 10.0.11345 earlier. The preview release build may be a 10.0.XXX build or we can see a 8.15.XXX build for preparing the system to take a 10.0.xxx build finally.
While most of us (enthusiasts) have becomes Windows insiders and are waiting patiently for that Windows 10 for phones first preview build to hit our devices, a new build that is much advanced than the latest Windows Phone 8.1 GDR1 build 8.10.14226 has been seen at WPBench. The new build that has been added to database some 9 hours back is 8.15.12492.0 and looks like a big jump over 8.10.14226.
So, the latest build 8.15.12492.0 may be a GDR2 build or even a preparatory build to the upcoming Windows 10 for Phones builds. If you check the initial build numbers of Window 10 for desktop, then till Build 9879, they belonged to Kernel version 6.4 or lower and with Build 10.0.9888 the kernel version upgraded to 10. So, this may be a initial Windows 10 for Phones version too that may be followed by Builds starting with 10.0.XXX naming scheme. We have also reported a Windows 10 for Phones build 10.0.11345 at WPBench earlier.