Windows 10 build 10586.306 (10.0.10586.306) spotted today. Just a few days ago Microsoft official released build 10586.240 for PC and 10586.242 for smartphones to the insiders for testing.
New build 10.0.10586.306 for PC and Mobile build 10586.306 TH2 was compiled on April 22, 2016 according to build numbers. If this build fixed all bugs in the last build then, this may be the new upcoming cumulative update both desktop and mobile.
Windows 10 build 10586.306 (10.0.10586.306)
— BuildFeed (@buildfeed) May 1, 2016
Currently, Windows 10 Build 10586.240 for PC and 10586.242 for mobile has been released to testers and hopefully these updates coming to end users on 3rd May as new cumulative updates. Microsoft is working hard on polishing Windows 10 experience for both PC and Mobile.