I not saying it doesn't happen, but the only analog I can find is when the PS2 was in short supply. If the theory holds that a sold out console drives people to buy other systems, then surely we should see a bump in Dreamcast sales when the PS2 was sold out. But in fact, it looks like there was no change at all in DC sales.
So while this effect may happen, it may not be large enough to make any difference in overall sales.







