A new Moto X phone may have just passed through the FCC recently with the model name listed simply as 10566 in one of the documents, though perhaps more telling is that another one of the documents in the filing specifically for the FCC label shows that the model number is XT1750. This may suggest that the phone in question is an upcoming Moto X device as previous versions of the Moto X series devices have had "XT" in the beginning of the model number, the most recent being the Moto X Pure Edition from 2015, which carries the model number XT1575, while others like the Moto X Style have the mode number XT1572. The increase from 15 to 17 could signify this as the next generation of the Moto X series, although with very little detail it's impossible to tell just yet what phone this may be.
One thing to consider is that the FCC Label diagram also lists "3G" and "8GB" which could be referencing the amount of internal storage and the supported network frequencies. Another part of the filing lists off supported network types as GSM/GPRS/EDGE/WCDMA/HSPA/HSPA+, but there is no mention of LTE, and a new Moto X would most certainly have this. The Wi-Fi support is also listed only as 802.11b/g/n, and a flagship device like the Moto X would be supporting Wi-Fi 802.11ac and not just b/g/n. There is some other detail that can be picked up from the filings. In the document for the FCC Label Location, the diagram shows the label on the back of the device, which is to be expected as most devices will have the FCC label on the back and under the material used for the body, or under that back plate if the battery cover can be removed. In this diagram, a large circular shape is depicted towards the top, which looks a lot like the camera modules that can be found on more current Moto devices, such as the Moto Z family of devices and the upcoming Moto G5 and Moto G5 Plus, both of which have recently leaked and carry a large circular camera senor module on the back.
Currently there are no Moto X devices which have this sort of camera sensor module on the back. Considering this, it's important to remember that there is no information stating this is a new Moto X, and all the information that points to it being a Moto X series phone resides in the model number that's listed on the label, and everything is just speculation at this point. Although the Moto Z is Lenovo and Motorla's current flagship set of devices, the Moto Z was stated as not being a replacement for the Moto X line, but rather just another offering that shares similar features. If there is a new Moto X device coming at some point in the future, chances are any announcements or official details about it wouldn't show up until later on in the year, as high-end devices from the Moto team usually come up in the Fall.