When it comes to new versions of Android, the Nexus devices tend to get things first before any other device. That isn't always the case now as multiple devices have gotten the update to Android Lollipop before some of the Nexus phones did, (although all of the supported Nexus devices have at least Android 5.0 now) and more recently with Android 5.1, one of the newest Nexus devices, the Nexus 9, has yet to receive an update to that particular version of the software. It is however still running on Lollipop. This makes it all the more confusing to hop on over to the audio latency support page for Android and see Android 5.1.1 detailed on two separate occasions, referring to something with the Nexus 7 2013 model, which is on Android 5.1 now, and the Nexus 9, which is still on Android 5.0.2.
The build numbers in question are LMY47W for the Nexus 7 2013 and LMY47S for the Nexus 9. What does this mean? We aren't sure exactly, but perhaps it means that these two devices will be the first to receive the updates. That doesn't make a whole lot of sense though, as we'd expect the Nexus 6 to get something before the Nexus 7 and it's possible that these references don't mean that at all. It's also possible that the figure shown on the page is simply a mockup as Google lists the table under a category called "example measurements," and examples are just that. Examples.
There has been some speculation about the next version of Android showing up at this year's annual developers conference, otherwise known as Google I/O, and if that's true and Google does show off the next version of Android this Summer, then this is probably when we'll see everything that has to do with Android 5.2. If this is the case then it stands to reason we'll likely see Android 5.1.1 sometime before then, which would have to put it sometime between now and the end of June which makes for a bout two and a half month period of time. Since 5.1.1 isn't that big of a difference in number, there most likely won't be any major changes to the system or the software, which would place it as more of an incremental update with bug fixes and improvements.