Just updated the OP to reflect the latest news/rumors on the KitKat upgrade schedule.
When will my phone/tablet get KitKat?
Nexus 4: OTA updates began 11/21
Nexus 7: OTA updates began 11/12
Nexus 10: OTA updates began 11/12
Galaxy Nexus: never
HTC One: Jan 2014
HTC One unlocked/Developer Edition: end of Nov 2014
HTC One Google Play Edition: OTA updates began 11/25
Galaxy S4: Jan 2014
Galaxy S4 Google Play Edition: OTA updates began 11/25
Galaxy S3: April 2014
Galaxy Note 3: Jan 2014
Galaxy Note 2: April 2014
Galaxy Tab 10.1: unknown
Moto X: OTA updates began 11/19
Droid Ultra: coming eventually
Droid Maxx: coming eventually
Droid Mini: coming eventually
LG G2: unknown