Note all my estimates are rough not exact!
I am thinking they will undervolt to keep a stick in the 2.5 watt range.
this was done with the antminer u-1 chip vs the the antminer s-1 chip. same chip lower volts and lower freq settings for the chip in the sticks.
same chip the usb stick is undervolted a bit and the the freq is set lower.
the antminer usb stick gets 2 gh pretty easy after that it is too hard on most hubs .
same is true with the cubes vs the be sticks the am cube pull more gh per chip due to more power and better cooling.
Still a usb stick in the 6-9gh range vs the 1.6- 2.0 range is a big boost.
You don't think they will design usb sticks for more than 2.5 watts? USB 3.0 is becoming pretty standard now and hubs are able to supply closer to the standard of 900 mA per port (4-4.5 watt). I wouldn't be surprised if asicminer provided adequet hubs for additional cost either.
I'm not sure AM will be focusing on the USB stick market anymore.