You don't need to wait for Cox to market another gizmo. You can purchase a wireless HDMI kit and connect it to your set-top box. The wireless HDMI kit contains a transmitter, which connects to your one set-top box, and a number of receivers, which in your situation would be two. You connect a receiver to each TV.
Of course, since you have one set-top box, only the program tuned (ABC, NBC, HBO, etc) can be transmitted to the other TV sets. Meaning, you can't simultaneously watch different programs on each TV.
Check out IOGear. It transmits at 5GHz, so there's less interference. It can be powered by the TV via its USB port, so you don't need to run a power cord to an outlet. While you're watching the other TV on the other level of your townhouse, the connected wireless receiver will transmit your remote control signals back to the transmitter. Meaning you can change the channel of the set-top box from the second TV.