Google announced Android L at Google I/O this year and it released a developer preview for developers to test the latest version of Android. But Google released the Android L developer preview to Nexus 5 and Nexus 7 only. Other nexus devices couldn’t get it.
But XDA-Developers have shown there magic here as well and they have ported the Android L developer preview to Nexus 4 as well. XDA Senior Members sykopompos and defconoi worked hard for many hours to be able to port the latest developer preview to Nexus 4. Some other members of the team also helped them to identify and come over the bugs that were being created in trying to port the Android L developer preview to nexus 4.
As this is an unofficial port so you can install it at your own risk if you are willing to taste the latest feature that Android L is bringing this fall. Instruction on how to install Android L on your Nexus 4 can be found here. According to developer warning “If you get the home button not working right then you need to do a full wipe to fix it.”