Well, you have to remember that THQ was in dire financial straits for quite a while before they finally went bust. Without knowing any numbers or anything, I'd be pretty comfortable betting on it being a little while before another big publishers hit the tubes like that. Based on the reports coming in, I'm surprised THQ lasted as long as they did. There aren't any companies that I can name off the top of my head that are hurting quite so badly.
As to who it's going to be when it finally does happen, that I can't say. EA seems to be the popular vote so far, but I think they've got enough to keep them floating, at least for a while. Yeah, they aren't doing much in the way of new IPs, but they've got a little bit of leeway with their currently established brands, so while they are going to need some fresh ideas sometime soon, I think for now they're okay.
If (or, perhaps more accurately, when) the modern military shooter bubble bursts, Activision are going to be in a lot of trouble, but again, I can't say whether that's going to happen anytime soon, and they might have enough going on to keep clinging to the black by the skin of their teeth, as it were. They're another company in dire need of some new ideas.
A couple of people have suggested Ubisoft, but I think that, with Watch Dogs (or is it one word?) on the horizon, there's a little bit of hope there. That title's a pretty big risk, but based on the reactions, it's very likely going to pay dividends. If they go the smart route, and back off the Assassin's Creed series for a while, now that Desmond's story arc has concluded, and put the money into some new and exciting titles, they'll be fine. But, like with Activision, if they plan on continuing to ride the Assassin's Creed franchise, then at some point down the road, possibly with the very next iteration, they are going to be in trouble.
Someone (or maybe more than one) mentioned Square-Enix, but while I know that their titles haven't necessarily being doing the best over here, I think (though I don't have the numbers to back anything up) that they're probably still pretty comfortable across the ocean. I'm fairly sure that they're still pretty highly regarded in Japan. But they have to drop their development times, or that arm of their business is going to be in trouble. And they have to stop announcing games six and seven years before they go into real development.
Capcom was also suggested, but, again, I think that, while North American fans might be getting pretty aggrieved with them, in Japan, they're still doing fairly well, (again again, no numbers to back up my claims, just vague assumptions based on conjecture). If not, honestly, they can just whip together another Street Fighter or Marvel vs. Capcom game, and they'd be fine. Throw more money behind Dragon's Dogma, maybe. Just stay away from, or completely restructure, Neverdead. And for the love of God, ease up on Resident Evil. Make it coherent, or something. At least make it psuedo-survival horror again.
Really, I think it all comes down to the plans the big publishers have for the next generation. If they aren't ready to adapt and change the market a little bit with the new consoles, and throw more than cursory support behind the PC audience, it's going to hurt them all. Who's gonna fall? I don't know. But I can bet it's gonna be spectacular.