After having been working on Releasing Stable builds for the Redstone branch for last couple of weeks, Microsoft is currently aworking on releasing an new Build for its Stable Branch Threshold.
The company is internally testing a new Threshold Build 10586.537 compiled on 21st July. This would be another Cumulative Update to be released both for Windows 10 PC and Windows 10 Mobile.
Currently we have no confirmation as to if any new features will be added, but going by the previous trend this could be another Cumulative Build do fix any bugs and improve the performance of the OS.
The new build 10586.537 could be released to Insiders on Threshold branch on 7th Aug which is the second week of August after the public release of Anniversary Update.
This new build could well be the last major release to the Stable (Threshold) Branch in the coming weeks for people who cannot update to Redstone.
Note: The release date 7th August is not yet confirmed by the company, hence please take this news with a pinch of salt and wait for an official confirmation from the company.