As was mentioned before in previous posts, the so called 'mirrorless market' is so loosely defined that it includes cameras with/without viewfinder, popup flash, hotshoe and includes cameras with various sensor sizes, etc. These permutations continue to be tweaked frequently by manufacturers.
Yet, I keep reading comments that Canon do not have a mirrorless strategy. In the midst of the various permutation that all the camera manufacturer throw out, why would Canon's move to throw a fixed lens into the mix be less of a strategy than the others?
As for zoom range, the G series already support tele and wide angle adapters... If the new G series camera would indeed have a 6.5x zoom lens (24-156mm equiv. according to some rumors), a set 0.7x and a 2x adapter would increase the range to ~ 16-312mm (sufficient for most people). Provided Canon makes the high quality adapters themselves.
On top of this, if Canon is able to improve the image quality and get it closer what the V1/J1 and m4/3 can do (judging from the 1/1.7" CMOS sensor of S100, I believe this is possible), maintain an f-stop of about f3.5 or f4 at the tele range so that it is not too slow when using tele-adapters and reduce the overall size of the camera, I think the G series is a viable competitor in the 'mirrorless market'. Oh yes, and add faster AF and operation speed to the list too.
As for sensor size, I am more practical. There is no way Canon can use a 4/3 like sensor without adding an elephant trunk of a lens to the camera. Thus, a 2/3" or 1" sensor would be enough to make me queue up overnight to buy the camera.