If the question is which company most has their back against the wall it would be Sony. They need the Playstation brand to be their gateway to the average consumer again, now more than every with ultraviolet, Music Unlimited, Movies Unlimited, their own streaming service on the way, Gaikai, etc..
If the question is which company will struggle the most this console generation it's clearly going to be Nintendo. They've been out for a year and Sony is about to pass their hardware install base in about a month. They have no third party support. Their first party studios are still struggling with the move to HD. Their core franchises now appeal to families and the core Nintendo specific fan, not the wider core gamer audience as a whole. They're clearly also not catching another Wii blue ocean with the Wii U. All in all the Wii U is something they should be hoping ends up at Gamecube levels.
But Nintendo isn't going anywhere. They'll bleed profits out of the Wii U, print money with the 3DS, and their first party titles will pretty much always recoup investment and then some. They'll take another crack at the console biz in a few years, though I hope they do so with a unified handheld/console single platform with wireless HDMI.
Lastly, if the question is which company is most likely to bow out of the industry then that's clearly Microsoft. They have activist shareholders trying to get them out already. They've moved control of the division to people who have no real loyalty or affiliation with the Xbox brand. They've got very little in the first party front tying them to the industry. If the Xbox One is a step back from the Xbox 360 and Sony regains a strong presence in the home console market Microsoft's next CEO could very possibly see flipping the Xbox brand and it's IPs off to someone else as the more profitable move. In reality I don't think anyone would want the Xbox brand itself if that happens, but they could likely sell the Halo IP and 343 together for a nice three figure sum. Forza plus Turn 10 would likely net a lower but still very respectable figure as well. They wouldn't have much else to cash in on, but those two plus the scraps of Lionhead, Rare, etc. would easily push a liquidation of the Xbox brand north of a quarter billion dollars in straight profit. That's a nice bump to hide new product R&D or a down quarter behind.