Changelogs come in all shapes and sizes. Well, maybe there is just the one shape, but many different sizes. A new tag for 5.1.1_r3 turned up a few hours ago in AOSP and we've generated a list of changes the change for those who would like to know what's going on. As it turns out, this update sets a record for the smallest changelog ever, at just one lonely commit. On top of that, it's specifically for the Nexus 6 (Shamu).
The lone commit in this release appears to be a bug fix for devices with encryption enabled. The adspd process has been set up to run with the encryption lock screen instead of after.
While the changelog itself isn't very exciting, it's clearly dedicated to the Nexus 6, which is a pretty good indicator that some OTAs and factory images should be rolling out soon. While other Nexus devices have been receiving Android 5.1.1 for the last few weeks, the Nexus 6 stayed on 5.1.0. We're keeping an eye out for updates, but it wouldn't be surprising to see the new version rolling out within the next few days. Since there are an assortment of different variants for individual cellular carriers, the OTAs probably won't come out all at once.
Keep in mind, the new changelog only shows the difference between r2 and r3. When the Nexus 6 is updated, it will also include the cumulative changes from previous updates (link 1, link 2, link 3), as well.