Some developers at XDA Developers have been successful at creating not one but two different ports of Android 5.0 Lollipop for Nexus 4. While the Nexus 4 does get an official Android 5.0 Lollipop update from Google after their official release of 5.0 updates this November, this is the most stable and polished Lollipop experience you could get on your Nexus 4 at present. If you would like to install Android L on the Nexus 4 then proceed by downloading linked Android 5.0 Lollipop ROM for the Nexus 4.
According to the developers this is bleeding edge and they have worked hard to squash out bugs, and is near perfect and is intended for enthusiasts, who want to try the Lollipop experience before Google releases the Lollipop update for Nexus 4.
The credits go to the developer team consisting of “sykopompos”, “defconoi”, “zyr3x”, “percy_g2” and “bpye”. The team has created two different Lollipop ROMs. The First one based on Google Nexus 6 LRX08 firmware consisting of entire Nexus 6 framework and S-build applications. And the second one is based on Official Google Nexus 5 Android L Dev Preview image. You can install and try out both these builds one at a time.
Both the builds do have the Lollipop features like pull-down quick settings menu, Material Design UI, the latest google apps, Android Runtime (ART) implementation which results in a jiffy fast system, new Lollipop fonts, better battery life and many other improvements. Since the builds are based on not-final code, one should expect some bugs and errors like the mentioned bug of Camera lag. But with not-final sources creating not one but two builds is a mammoth task and kudos to the team for being successful in this.