Uh WTF? There a bunch of Moto compatible vendors... Pace is a big supplier of new equipment for Comcast right now. They make the RNG110, an RNG150N model, and the current X1 DVR and a revised model that will be shown at The Cable Show in June.
There are upcoming products from Humax and Arris (not the recently bought Motorola division, Arris itself) too.