if everything runs the same with the new r-box as it does with the older smaller r-box, you shouldn't have any trouble running 6 or more. i have the raspberry pi model B+ and 5 of the older r-box ( 32- 37) and i have all 5 plugged into the blackarrow break out board (which supposedly can handle up to 10 of the older r-boxes but it actually looks like it can handle more )and running off a 7 port powered usb hub. the hub is only plugged into one of the USB ports on the raspberry pi. still have 3 left to plug more stuff in.
I do not know how the new r-boxes plug into the breakout boards. but i'm assuming you can run at least 6 , maybe 8 off one board depending on the board you have. and plug them all into a powered USB hub. and then plug that hub into the raspberry pi.
depending on the model of Raspberry pi you have, you'll either have 2 usb ports on it or 4. so you should be able to repeat the above hardware config as many times as you have usb ports on your raspberry pi. So based on the numbers and enough power and breakout boards to handle them all. you shouldn't have any issues running 12 - 32 ( depending on Pi model)of them off a raspberry pi if it can handle that many USB devices running at once. i don't know what the max is the Pi will recognize.
i haven't seen a good description of how to run the raspberry pi off a breakout board yet. so i keep it under its own power using an ac adapter. same with the powered hub.
next month i plan to order 2 of the new R-boxes off you crazy guy. from everything i've seen, you have the best prices around.
thanks for info but I ordered the one bringing me to 3 r-boxes. it will be enough for now.