They'll all stick around.
If you read my other thread a few weeks back regarding the mobile OS being more important next gen, you'll see that its just changing, not ending.
All three will have lower cost, shorter life "consoles" that will also enable smart OS full features and will be joined by Apple's TVs and iTVs as well as other Android OEMs.
3rd party games will be on everything, Android will rule it in marketshare, and Nintendo/Sony will likely have variations of Android with their own respective store fronts.
So in the end, the number of 'gaming consoles' will actually grow quite significantly and the big 3 won't reach 100m type sales as the pie is cut up to smaller slices. But that just means we as consumers win.







