Can you connect a signal splitter to a microcontroller to get more motor ports?
No, not that we can support. As stated in the downloadable documentation located on the Product Page: It acts as a “dumb” replacement for the Vex Microcontroller. This module requires the Vex Transmitter & Receiver Kit (TX/RX), as well as a 7.2V Battery to operate.
Is there anything coming out that can perform this type of function?
**If you can write Code to create a PWM signal from a Digital Output Port, you can use that signal as a PWM Input to the Power Expander. So you could have 4 more motor ports via a Power Expander at the cost of 4 Digital Outputs.
If you can write Code to talk serially to another Microcontroller, then you could add another Microcontroller and send it commands from the “Main” Microcontroller - receiving commands from a Transmitter.
Unfortunately we can not support these tasks. I also suggest you post this question where the VEX Community can share what they have done.**