Although unlikely both PS3 and 360 could overtake the Wii. It is all about who has the game changing software and how well its countered. For example say MS or Sony find that system selling exclusive that appeals to the masses. I don't think either of them have had that yet. Halo 3 is probably the closest thing the Xbox has had as far as system sellers this generation and it already appealed to the 360 fans anyway. Wii has Wii Sports which has everyone over the age of 40 addicted to it like crack and also Wii Fit. Wii console sales would be dead in the water right now without Wii Fit as I do not know one single person who is currently buying a Wii without the intentions of picking up Fit in say the last say 6 months or so. And MS and Sony both have not had anything to counter that game in any way.
Yes PS3 is off to a much slower start then almost anyone anticipated, but to be fair its still selling well if you compare it to almost any other console. The 360 is also selling well and seems like it is really starting to gain some momentum, but it hasn't significantly widened the gap from the 1 year head start either.
There are really only three groups of people that own the Wii.
The hardcore Nintendo fans, who do buy alot of games, but mostly prefer Nintendo published software as they have arguably some of the best franchises of any console.
The hardcore gamers, people in this group own at least 1 other current gen system (360/PS3) they like primarily Nintendo titles and other exclusives for the Wii, but will buy all multiplatform titles (Madden) on their other system. Every 6 months or so we will dust it off and buy a new exclusive.
The Family people, these are people who have bought the Wii because of its family oriented and healthy image. After the initial purchase it is fun for a week, so they go to the store and buy some more games then after a month or two it gets old and it just sits there unless there is company over visiting. These people don't buy many games to begin with.
A good example of how PS3 wins this generation is if Blu-Ray somehow does what DVD did, DVD was out for several years like 4 years before it started getting adopted by the masses. If the masses started clamoring for Blu-Ray PS3 quickly becomes the fastest selling console.
