Soni sent out the word on Google+, even though the message was definitely Twitter-length. It was a short message saying, "Step 1 of rollout. Dev editions, other carrier versions rolling out in days." Although we haven't had official announcements from any other carriers, the assumption has been that the Moto X would hit Verizon and Sprint before the end of August.
It's unclear if the "dev edition" that Soni mentions is the version that will be sold directly through the Google Play Store. We know that the Moto X will be sold in the Play Store, and that it won't be a Google Edition device. All devices sold through Google Play are sold carrier unlocked, but not necessarily bootloader unlocked as you'd want in a developer device.
source: +Punit Soni