The assumption is that the number of 'strips' (thats what a 'channel' is in digico speak) would increase. The SD9 has 24 physical faders with 4 banks, so thats 96 places to put a channel. So obviously not enough to have every channel on the surface, but I guess they would have to implement some kind of additional layer
The question is how many of these 96 channels will be Flexi channels. I think you could easily incorporate one of the user buttons to make a 2nd fader layer if that's the route they take.
Since they only specifically mention the SD7, SD5 and SD9 in the press release, it begs the question of what is in store for the SD10, SD8 and SD11.