Until Microsoft shows it is capable of figuring out the mass market this will never come to pass. Nintendo has more then once captured the mass market (NES, Wii, SNES kinda) by appealing to kids who in turn got some adults to play by creating the kind of meme that made it to the nightly news and increased exposure. Sony has more then once captured the mass market with the PS1 and PS2 mainly through later in the consoles life casual sales and again, by buzz from gamers and kids trickling into the main stream.
MS on the other hand has never shown at all that it can break through that wall and reach the main stream, its still the gamerboy box that sells pretty narrowly to gamerboys (I know all kinds of people who own a PS2 and/or a Wii but a VERY specific crowd owns the 360) which is why even with a huge price cut it can't sell mass market penetration numbers like the PS2 or the Wii (even at the lowest price point the 360 was well under half the Wii's sales or the PS2's sales when the PS2 was a few years old).
This isn't to say Sony will win again, who knows on that count, but it seems pretty clear that it will be Sony, Nintendo or a new third party entry from another company (maybe Apple if the iphone keeps taking off, they could leverage the already decent processor power of the apple TV or even the developer collaboration singular box from a EA/Activision/ect team that EA keeps talking about).
Basically Microsoft has never captured the publics imagination on any consumer products ever. Not Windows mobile, not the Zune, not the Xbox, not Surface...nothing. They just are not the kind of company that makes a consumer product that everyone wants to have and everyone talks about. When they come out with motion controls or free online or whatever they take from the PS3 or Wii Sony and Nintendo will come out with something better and revolutionary leaving MS fighting for 2nd with whoever the next runner up is again.
PSN ID: ChosenOne feel free to add me
