MDC1460 Dual Channel

I have two MCD1460 controllers and would like to convert both to dual channel operation. Can I just update the firmware to MDC2xxx to make that happen?

Unfortunately you cannot. There is only hardware for a single motor channel in that controller.
the first digit after the three initial letters in the model number actually designates the number of hardware output channels on the controller. Any single channel controller that has 2 hardware output channels (our "S" controllers, such as the FBL2360S) can be converted to dual channel with firmware. But not the MDC1460.