After the launch of the PS2 there have been sold one PS2 every 3:rd second 24/7. So assume that after the GC and x-box launch that figure goes down to one every 5 sec.
That will result in 6.2 million units sold following the 12 month that follows after the GC/x-box launch.
Lets assume that the PS2 will have sold 13.8 million units(so no xbox or GCfans says stuff, "It has not sold that many!!" a.s.o), that will result in a total of 20 million units sold by Nov 2002.
Assume that the x-box will sell with higher speed than the PS2, lets say 1 x-box every 2 second, that will result in a first year very impressive number almost 16 million units!!!
Assume that the GC will sell like the x-box. 16 million GC.
This will result in this numbers by Nov 2002:
PS2: 20 million units.
x-box: 16 million units.
GC: 16 million units.
Then it will only take a couple of month before the GC and the x-box has sold more than the PS2.
It could happen but not very likely.
IMO I think that the PS2 have sold around 19 million units today= 1 PS2 every 2.5 second, the number of will likely be way better because the production is set to 1.8 million units / month = 1 PS2 sold every 1.44 sec. I don´t think Sony makes more consoles than they can make.
If this figure goes down to 1 ps2 every 3 second, will result in 11 million units the year that folloews after the GC/x-box launch. That gives a total of 30 million units by Nov 2002 (very likely IMO)
I think that the x-box will sell about 5 million units the first year and GC 5 million units. The numbers are pretty high, half what PS2 sold the first year, it is very high numbers but not impossible.
That will give this situation Nov 2002
PS2: 30 million (75%)
x-box: 5 million (12.5 %)
GC: 5 million (12.5 %)
The next year after that the % share of the PS2 will probably go down to something like 60% or so giving numbers like this:
Nov 2003:
PS2: 37 million (60 %)
x-box : 13 million (21%)
GC: 11.7 million (19%)