According to a post on the Google Issue Tracker, it looks like some of the new camera APIs introduced in Android 5.0 will not be available on the Nexus 4, like full manual controls and DNG support. This is apparently due to hardware constraints with the Nexus 4 that prevents the support for new camera features.
Google’s post reads, “Unfortunately, the Nexus 4 will not be updated beyond LEGACY camera2 level support. Its hardware and firmware were not designed to support the full feature set provided by camera2, including manual controls and DNG support, and such support cannot be added retroactively to it.”
Interestingly enough it seems that the Nexus 9, despite it being a new piece of hardware, will be missing some camera features too, like DNG support, but will still get manual control. In the meantime Nexus 5 owners can breathe a sigh of relief as it looks like your handset will be getting all of the new camera features.