Microsoft officially announced Windows 10 Anniversary Update on August 2nd but many users are still waiting for the update. It appears this is completely normal and no reason for concern, ZD Net reports Microsoft indicated that it will take up to three months to reach all users.
The reason for the slow roll-out is because Microsoft wants to keep close tabs on what's working, the software giant extensively uses the Windows telemetry data to figure out which computer hardware and software combinations can cause issues so it can fix these problems before they hit a broader audience.
Microsoft is throttling delivery of Windows 10 Anniversary Update, and, presumably, future updates, so company officials can keep tabs on what's working and not as the update rolls out to the many, many permutations and combinations of Windows machines where it's qualified to run. This is part of the reason why Microsoft is obsessed with telemetry and has been for the past few years.
If you want to install Windows 10 Anniversary Update sooner, you can force its installation by using this update tool from Microsoft.