PS4: 110m; it's going to continue selling very well, but don't think it'll be PS2 ubiquitous
Switch: 80m; too early to tell, could very well be higher, depending on whether it can recapture the 3DS audience
3DS: 75m; the system has peaked, plus Nintendo will be keen to move support to the Switch after this year
XBone: 45m; they'd be lucky to get this high, will probably try to cut the generation short, again