Yes, you're probably right, but I can't think of another japanese company who is big and influent enough, or has the resorces, to take Sony's place and compete with the Microsoft giant. (maybe Nintendo ^^). 

Panasonic, for example, makes excellent products but they are sure a lot smaller than Sony, not to mention inxperienced... they have already failed once in the home console market.

So now you have changed your tune to " They live and die the most by their systems. Microsoft and Sony have sustainable business elsewhere to prop their companies up if things go South for three consecutive generations"

Changed my tune? I said that in my first post.  Lol.

Excellent. So lets assume that the Wii U sells 34 M (ie about 30% of the final sales of its predecessor), and lasts for 5 years, that will take us to late 2017, then the Wii U 2 comes out and sells 21 million, leading to the Wii U 3 releasng in late 2022. Assuming it flops as well, then we have hit three consecutive failoures and thus we hypothesise that, as early as the year 2027, Nintendo may leave the home console business by not creating a Wii U 4! The end is imminent.

I never said the end of Nintendo is imminent.  I just said they are the most likely to be the 'next' to leave.  The wild success and profit of the Nintendo Wii has saved Nintendo for a forseeable timeframe in my estimate.  However,  Nintendo has no assets or sustainable business beyond video games.  Where as Microsoft and Sony have far more resources at their disposal for a bad streak of generations. If Sony wanted to adopt a strategy similar to Nintendo, they could produce the components of a PS3.5 at a bargain rate similar to how Nintendo created a GC 2.0 with the Wii.  And it's likely the strategy they would take if it ever came down to it. 

And yes, they only got through the N64 and GC years (making a profit every single year) because of the success of their portables. Well, lucky for Nintendo, the 3DS is to be the fastest selling console to 15 million units ever, by 2 months. Vita hardly looks like it's going to shake that dominance.

What were their profit margins on GC and N64?  I don't care if they ended up in the black if their profits were minimal.  Because that's precisely my point.  Minimal profits means Nintendo can hardly compete moving into the future.  Nintendo needs to make a profit because otherwise they are going to come to a stand still.  They don't have sustainable business beyond gaming.

Sony could drop handhelds tomorrow. That doesn't mean they're going to leave the gaming industry.

Since, Nintendo sells consoles at a profit or very small loss and their software are so universally popular they are currently nowhere near getting out. Even if Wii U only sells 30 million, the console will sell enough hardware and software for them to make nice profits. They don't take big losses on consoles like Sony and MS do. Smart business for a gaming-only company.

They are a  very smart business.  However, if they did release a terd or two of a console and a terd of a handheld and sold a paltry amount, they don't have the sustainability to survive much of that.  It's the same situation as Sega, except they are far better at managing their business.

Based on the current state of the three the only one who would be likely to leave if they failed next gen is Sony. If Vita doesn't do as well as PSP and if they take even more losses with PS4 thanks to stiff competition from MS and Nintendo, that could very well drive them out of the industry. It doesn't matter if they have other branches when those  are not doing well either. If they reach a point where the gaming sector is dragging them down even more, they could very well cut it out (though it would make more sense to cut something else out instead since their gaming sector is one of the most profitable).

Again, as gaming is one of their most profitable sectors (Even in colossal failure that the PS3 generation has been for them), it's completely unfeasible barring Sony going under that they would abandon their gaming division.  Maybe a poor sector of their gaming division (Handhelds?).  

MS has large amounts of cash and their long-term goal is to become the entertainment centre of people's living room which they seem to be on the path to currently. So even though they have taken so much loss since coming into the console business, I can't see them getting out unless they reach a point where they have taken so much losses they decide it isn't worth it anymore.

Microsoft isn't immune simply because Microsoft hasn't dipped their feet all the way into the gaming community.  I could see another Xbox type generation really sinking, discouraging them.  MS doesn't have the first party studios like the other two.  They don't need to sustain losses, they could easily drop the gaming division from a business standpoint.

I just think they've provided enough competition in the market to remain viable and they have the money to take some hits and they're a large enough Corporation that can eat these hits to some extent.

Panasonic isn't big enough to buy Sony, but here the hypothesis wasn't of Sony sinking, but just abandoning console gaming and selling the PlayStation business, and Panasonic is big enogh to buy it. Lack of experience could be easily overcome buying Sony's whole PlayStation HW and SW business.

If Panasonic and Fujitsu aren't big enough, Mitsubishi surely is, anyway.

Or Panasonic and Fujitsu, or another big Japanes company, could form a joint venture to acquire the PS brand.

The last possibility I can think about is Sony itself forming a joint venture and rescuing but keeping partial control of PS.