We're getting less and less exclusives? Last time I checked PS3 had more first party exclusives, and 360/Wii have more exclusives then their predecessors in general.
Also really? No option for no one being eliminated, or a 4th party joining in? I really doubt anyone will get eliminated, especially if console generations continue to last longer (giving more incentive to buy a second console). I think this is especially true when you realize that the 360 and PS3 are the best selling 2nd and 3rd place systems in their generation, and they did this by a significant margin (before the best selling second places only had about 30 million)
I don't think anyone will get eliminated. I think Nintendo will dominate by getting 3rd party support while maintaining a strong 1st party portfolio, and releasing an affordable system which still has Call of Duty support. Sony and Microsoft will battle for second again, especially since they will be entering the generation late, and I think Valve will work with Apple and make a 4th console. Valve is Microsofts main compeditor for PC's, and it's only a matter of time before they make a Steam console.
I think there will be 4 home consoles next gen.
However.....Sony might pull out of the handheld market, or at least really drop far behind, with the game lacking PSV. I also hear a lot of talk about Sony's stock going down, so maybe, just maybe, Sony might stop producing Playstation systems, and give Valve the rights to all their studios (if Sony goes Bankrupt).