The delays from one carrier to another are most likely caused by the carriers themselves, rather than Motorola. Motorola has been extremely fast with updates, but this one, albeit a minor update, has taken longer than most. Even Motorola's VP of Product Management, Punit Soni recently bemoaned how carriers can cause delays in the process, no matter how much Motorola may push to get updates out to users quickly.
Still, as these things go, Motorola is still well ahead of other manufacturers. With the soak test invites going out today, it is reasonable that Moto X users on AT&T should expect to see the official Android 4.4.4 update rolling out to everyone within the next week or two.
source: Android Central