Rob: yes, we worked a lot on the connection system, so there are already these kind of modules:
3 wires: Same pin-out as RC/Servos and other standard analog and some digital sensors. The beacons, buzzers and other low current actuators that needs GND/Vcc/Data use this connector too.
4 wires: These connectors are reserved for intelligent sensors with Tx/Rx lines, such as ultrasonic (we are designing an open source one reprogramable with the Arduino IDE).
2 wires: These connectors are for motors, up to 1 Amp. continuous (we use 0.35 mm^2 cables, which is aprox. between AWG 22 and 21 so they can carry this current). The DuinoBot boards has two of these connectors for their HBridge outputs.
Also, we defined a 5 pin connection, which is for connecting boards to comm mocules, but with Reset line. So, a brain (like a DuinoBot) can be reseted from a comm module (like the FTDI or the Bluetooth module) for bootloading.
Regards,
Julián