More than likely we will be seeing Android 4.3 officially unveiled and pushed out to the Nexus 4 sometime next. However, if you are a bit impatient about that, then you don't have to wait. A leaked version of Android 4.3 for the Nexus 4 has apparently hit the web. The build is JWR66N, and was supposedly on a phone bought on Craigslist from a Googler. Here's a quote with a few relevant details, followed by a download and source link,
Download link: https://mega.co.nz/#!JYomQCDA!XQvQdk...7H_OJlgerXviVkThe build is in TWRP backup format so you will need the custom recovery installed. Currently the radio and bootloader are missing, but will be added soon. We also donít know how final this firmware is so there could be other bugs.