According to T-Mobile's website, an Android version bump is due out today. While details of specific changes are sparse, the support documentation for Nexus devices very clearly notes a release date of June 2nd for the software.
Sprint may have jumped the gun with its own outing of a 4.4.3 update about a month ago, but all indications point towards today's date marking the beginning of a staged-rollout from Google.
As stated, Security enhancements and Various bug fixes are headed our way. While not the most exciting of changelogs, we can at least expect a fix for the battery-draining camera daemon bug.
Other speculated changes include fixes for random data drops and an improvement in camera shutter speeds. If Sprint's previous changelog is to be believed, compatibility for the 3rd-largest US carrier's new Spark data connection will be added as well.
Your phone will notify you when it has downloaded the update and readied it for installation. You can simply wait for this notification to appear, then follow the prompts for installation.
If you'd rather check for this update manually, just head into Settings, then About Phone. Tap System Updates and hit Check Now from the following screen.
Since Google updates its Nexus devices in a staged format, the update may not show for you today. Only a small fraction of users will receive the update on the first day of a staged rollout, with the number of users who receive it increasing each day.