Duration of System Update - Nexus 4 (after download) - 4.4.2 to 4.4.3?
I had the same issue, after giving up on waiting more, I restarting the phone.

After reboot, the update started from where it was, and finished as originally intended.

To restart the phone, hold Vol-Down + Power for a few seconds.

Posting answer as the OP only posted solution in a comment.