The Windows Team at Microsoft are still hard at work on Windows 8.1 as they develop at full speed towards their deadline date. Windows 8.1 is expected to hit RTM sometime this month, and recently build 9472 was compiled. The build was compiled on the 29th of July, just a few days ago as of typing this.
As Windows 8.1 is expected to be released to OEM's at the end of this month, RTM is to be expected within the next few weeks.
It's clear that the Windows 8.1 RTM won't differ that much from the Preview, as the Windows 8.1 Preview was pretty much feature complete when it was released. Bug fixes and App Updates are expected to be the highlights between the Preview and RTM. For example, apps like Mail and People will be getting a complete UI update which adds additional functionality.
For those tech-savvy readers, the full build string is 9472.0.winmain.130729-1720.
Microsoft have compiled 41 additional builds since the Windows 8.1 Preview, and are expected to artificially jump to 9600 when RTM is completed. Microsoft have done this in the past with Windows 8. The OS was pretty much finished at around build 8888 but the Windows Team had to artificially jump to 9200 due to the way the build numbers are compiled.