Microsoft has released Windows 10 RTM build 10240 to Windows Insider members on both the Fast and Slow update rings. To get the new build, go to Start > Settings > Update & Security > Windows Update > Check for updates. Windows 10, will finally released on July 29 for general public.
More updates may come before Windows 10 officially launches on July 29, as Microsoft Gabe Aul said in a blog post that "this build is one step closer to what customers will start to receive on 7/29."