Android L
Android L Developer Preview has been ported into Galaxy S4 LTE. Wikipedia

Finally, the Android L Developer Preview port is now available for the LTE enabled Galaxy S4 bearing model number GT-I9505 running Snapdragon 600 quad-core processor.

Senior XDA member, ISF, claims to have successfully ported the Android L Developer Preview to the Galaxy S4 LTE. Nevertheless, the developer notes that it as an experimental port.

Currently, the port only installs Android L and shows the boot animation, reports Android Soul. The port still needs a custom Android L kernel for Galaxy S4 and system tweaks to become functional.

The port is in its alpha stage and has been receiving a number of fixes.

Head over to the development thread to know more about this port. Unfortunately, there is no Android L Developer Preview download link available for the Galaxy S4 as it appears to have been removed.

Hopefully, the developer uploads download link for those who wish to run Android L on their Galaxy S4 prior to the official release.

Like the Galaxy S4 LTE, a couple of other non-Nexus devices to receive Android L port are HTC One M7 and LG Optimus G.