Update: Good news! Looks like the 4.4.4 soak test is now underway on Sprint. If you're part of the Motorola Feedback Network, you maybe might possibly have access to it now. Hopefully everything runs smoothly so the full update will go out to all users soon.
We've received reports from numerous users that Sprint has started sending out invitations to a soak test of a future update for its version of the Moto X.