Motorola pushed Oreo update to Moto X4 last month - both the Android One version and the standard model got the system update. According to support specialist from Lenovo forums, the new Android should be already be hitting retail units in the US that are not part of the Android One program.
The deployment to retail Moto X4 units may have started, but owners should be patient. According to the Senior MotoAgent, OTA updates depend on model, country, and carrier. Still, keep an eye on your notification area in case the update prompt appears.