Stop and think about what you said (the bolded part). If Sony, MS or Nintendo leaves home consoles there sure as hell won't be anyone to "fill the void". It's too risky business, the game industry is a joke as a whole and there are very few who are actually doing great in the industry commercially.
Why would any steady company like Samsung etc. want to mess their bed with this shit? It's not the same industry it was 10 years ago. A lot has changed and a lot for the worse.
Its a multi-billion dollar industry. Nintendo is a sizable company that lives entirely within this one segment, and they have literally billions in the bank and turned consisent profits every year for entire decades at points.
Microsoft made enough money on the X360 last generation to basically off-set the original Xbox losses AND all the shitty losses they took on various other entertainment division failures (like Zune).
The business model (being a platform holder who makes most of your money off royalties) is exactly what Apple, Google, and Valve currently offer. We currently know that Apple is looking to roll out gaming on AppleTV and that Amazon is building a gaming box as part of their push into that segment.
So you really think that should MS leave not a single one of them would see a niche they could thrive in? Would they stop making $500 hardware that they then sell for $400 eating the loss? Probably, but they wouldn't ignore one of the most lucrative forms of media from a royalties standpoint to a single company.
Further, they can't from a strategic standpoint. Sony has made it pretty damn clear that long term they're gunning for the Apple storefront and Google Play. They have Music Unlimited, Movies Unlimited, Gaikai in the pipeline, their own online music outlet, their own online movie outlet, their and their own online games outlet. The near term emergence of cloud computing will make online storefronts by far the primary source for media of all kinds, and owning the storefront will entitle you to the lion's share of the profits.
Sony became painfully aware of this after iTunes gobbled up their dominant position in the music industry while they where bitching about piracy and Napster. They've positioned themselves to cut everyone else off at the TV via Playstation. Microsoft is their biggest competitor on this ground and so far this year has been shitting their pants. Apple, Google, etc. aren't far from getting into this industry regardless via some sort of box or in-tv circuitry. Microsoft leaving would open a gaping hole they'd all rush to fill.