Deering arrived at these figures "by triangulating Screen Digest and IDG data. He also took into account factors such as the growth of hi-def and the grey gamer market, the emergence of new game engines and increasing ubiquity of wi-fi access" and we imagine he probably tried out runestones, tarot cards, and a ouija board just to be safe.
What's impressive are the sheer numbers alone. He predicts that by 2011 both Sony and Nintendo will have sold 230 million total machines each (Sony: PS3 + PS2 + PSP; Nintendo: Wii + DS), and that the Xbox 360 will have reached a user base of 40 million. The only thing is, the 360 has already reached the 20 million mark, so he thinks it'll continue on that track for the next three years at exactly the same pace, due to the "set-top box hi-def phenomenon."
He also concludes that the number of potential gamers will reach 2.5 billion due to the amounts of consoles, computers, and mobile phones sold, to which we say... isn't everyone a potential gamer?