It looks like T-Mobile customers who want to nab the new Moto X will have to get it through other channels than T-Mobile. The device will not initially be sold in their retail shelves. They made it clear that the device is compatible with their network, so it will eventually be offered in their retail channel; however, they have no specific information as to when that will be. Here's a quote from the T-Mobile Chief Marketing Officer Mike Sievert,

“The Moto X optimized for T-Mobile’s 4G LTE network will initially be available through Motorola’s channels. We do not plan to stock Moto X devices immediately in our stores but are working closely with Motorola to make the Moto X a great experience for T-Mobile customers. Any news about distribution in our stores would come at a later date.”
So, that isn't very clear, but it appears you can still get the device for T-Mobile, but you will have to order it directly through Motorola. We will continue to research this and share more info when we have it.

Source: MotoXForums via AllThingsD