Update:

And we have some official confirmation to go with for a new Windows 10 Mobile build in the 105XX range, that will not come today but still very soon, as per Gabe Aul.

build 10512A new Windows 10 Mobile build may be pushed as early as today, if one of our tipsters has to be believed. If it doesn’t get pushed today then tomorrow it is kind of certain for a new build as per the tip. Though take it with a pinch of salt!!

The build number is not entirely certain but it may be in the range of 10.0.105XX and a new leaked build in China is a likely candidate. The build leaked in the above screenshot is 10.0.10512.1000.

If the latest trend of minor changes in latest builds continue we may not see many big changes in the upcoming build but it may be more stable and polished than current build 10166.

You can read all about the Windows 10 Mobile upcoming / rumored changes and detailed changelog by clicking here.