Microsoft last pushed Build 15007 for Windows 10 Mobile and Windows 10 PC  to Windows Insiders in Fast Ring. However, the company has already started testing new update for Windows 10 PCs and Mobiles.

 

Now, a leaked screenshot hints about the Build number for this preview build. As per this leaked screenshot Windows 10 PC / Mobile Build 1501o may be the next. This build is not yet listed on BuildFeed however.