The new firmware version is traditionally first appears on Google-devices. Its first get the Nexus 7 (2013) and Nexus 9.
The company itself has not announced the release date of Android 5.1.1, but is determined by circumstantial evidence. Observant users noticed in the tables with the testimony of audio delay, posted on the official web portal of Android, the Nexus 7 and figures 9. Among other things, it was obvious that the device tested already in the firmware Android 5.1.1. This means that users will get the update system in the very near future.
It is unknown what innovations will bring the new firmware, but most likely major changes will not happen. You can predperemestit that developers simply eliminated some bugs of the previous version.