240mil is beyond insane, last gen there were 120mil PS2s lets say that 20mil had been replacement consoles, people might have dropped theirs, some might have broken. Now thats 100mil, take off another 10mil for people who bought the new slim design one, thats 90mil different owners of the PS2. The GC sold 20mil the xbox sold 24mil, out of those numbers lets say 70% owned another system, so thats only 14mil gamers last gen that never owned a PS2.
Last gen saw 104mil different people own a system, so far the wii has sold 11mil, out of that number 10% never owned a system last gen. So we only have 10% new users after 9months. But lets take this to the extreme and say that the wii is able to make 40% new users this gen.
This gen will see 145.6mil gamers at the very most, this also assumes that all Sony/xbox fans will buy the wii at one time during this generation.
This also assumes that Nintendo can make this many systems, which i doubt they can. Sony was able to make 120mil PS2's due to its massive industry of other products it makes and was able force those factories to make the PS2.