When the Nexus 4 was launched, it was not supported by AOSP and its source code was not released. JBQ said support wasn’t available at the moment, but we can’t imagine a Nexus device without AOSP support. Luckily, at least part of the source code was released to the Android Git. It lacks all driver binaries, but the code is there. If you wanted to build a ROM, you could use the drivers from Nexus 4 system dumps, modify the source code, and release fully working ROMs. It’s a good alternative while the Nexus 4 is not an AOSP supported device. ROM chefs, get going!