It's becoming to be like fifth generation era where there was Nintendo, Sony, Sega, Bandai, Panasonic, Commodore, Atari, Philips, NEC, FM Towns, Apple, Casio, SNK...only Nintendo and Sony did that well. Sega did fine in Japan though because it had pretty damn great 2D arcade games but in the West it bombed as it didn't get those localised.
Someone is going to bow out of the big three in the next gen, I see it being Sony sadly to be honest. Nintendo has the 3DS & Pokemon to live on and can just regroup if the Wii U continues to do "ok" sales, even then the Wii U will make them profit.