Folks on Sprint who own the Google/LG Nexus 5 will get another version of Lollipop later this week. Sprint themselves revealed that Android 5.1.1 “LMY48B” will be rolling out to the device very soon. According to their announcement, it should have already started pushing out on May 11th, but it's obviously a bit behind.
The only detail given on what this update does was labeled as “security enhancements.”
Source: Sprint